Control and surveillance system for prepayment public telephone apparatus

ABSTRACT

In an apparatus, a passive equipment is designed to transmit informations on a telephone line, indicating energization of the apparatus, hook-off condition, insertion of a prepaid credit, collection of part of the credit, or operating anomalies. An active equipment is located to be inaccessible to the public and close to the central office, and performs establishment, holding and management of telephone communications seized by the apparatus, in order to perform a permanent check on the conformity of various phases of a communication and to ensure dependance of continued communication upon information transmitted by the apparatus. On the telephone line, the information is transmitted within a frequency band differing from the communication frequency (voice) band so as not to affect the communication signals.

CROSS REFERENCES TO RELATED APPLICATIONS

Applicant hereby makes cross references to his Patent Application PCT/FR85/00 331, filed Nov. 22, 1985 and claims priority thereunder followingthe provisions of 35 U.S.C. 119.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control and surveillance system for aprepayment public telephone connected to a telephone central office viaa telephone line. A communication may be prepaid by means of coins or acredit card.

2. Description of the Prior Art

The problems involved in the management of public telephones in the faceof increasing acts of vandalism and fraud lead to a series ofobservations calling into question current strategy and highlighting theweak points of known systems. The system embodying the invention isdesigned taking account of the following observations.

In order to combat fraud were developed increasingly complex publictelephones, becoming more and more expensive and required increasinglydelicate and costly maintenance. To each type of fraud there is aparticular type of defense which, on the one hand, increases thecomplexity and the cost of the apparatus and, on the other, leads thedefrauders to resort to increasingly powerful and damaging means. Atpresent, the losses due to vandalism and fraud are considerable. As anexaple, about 20% of telephone traffic carried by public telephones isfraudulent. Repairs due to vandalism and the loss of revenue due tofrauds have reached several hundred million Francs for a total of morethan one hundred thousand apparatuses.

Remote surveillance of these apparatuses might be based on the analysisof the number of basic charge unities elapsed during a predeterminedperiod for each public telephone, as described in European patentEP-B-0,004,497. In this case, remote surveillance only notes theanomalies after the event and does not allow immediate action. In othercases, such as the use of signalling contacts, remote surveillance islimited since it is dependent on the normal intervention by thepersonnel; it can therefore only be used outside service hours, thusreducing its effectiveness.

From the point of view of management and daily operation, the systemscurrently in service offer the following disadvantages:

Operating anomalies, faults and unusual or fraudulent acts by the userare neither detected, nor identified, nor even signalled.

The collection of revenue by coin box collection staff poses aconsiderable verification problem, inadequately dealt with by theexisting procedure which is inefficient and cumbersome owing to the factthat the coin boxes are sealed. Memory coin boxes, such as described inEuropean patent application EP-A-0,041,457, provide a solution to thisproblem, but at the price of a complex, inflexible and costly operatingprocedure.

Accounting and technical operating data concerning the apparatuses arecurrently analyzed by means of hightly dispersed ressources makingcollection and utilization of these data difficult and laborious. Thecollection and analysis of the various operating indicators are socomplex that in practice, the control services use this ressourcesparingly.

OBJECTS OF THE INVENTION

The main object of the present invention is to provide a control andsurveillance system for at least one prepayment public telephoneapparatus, remedying the disadvantages mentioned earlier, concerningparticularly fraud and vandalism. In particular, the invention aims todistance as far as possible from the reach of the public, means involvedin the establishment, holding and management of telephone communicationsseized by the public telephone and to check permanently, and in alocation inaccessible to the public, the conformity of various phases ofa telephone communication, with the continuation of the communicationbeing dependent on informations transmitted by the public telephoneapparatus.

SUMMARY OF THE INVENTION

Accordingly, a control and surveillance system for a prepayment publictelephone connected to a telephone central office via a telephone line,is characterized in that it comprises a first equipment included in saidapparatus and connected to the telephone line for transmitting signalsindicating particularly energization of the apparatus, a hook-off, aninsertion of a prepaid credit (coin or card) into the apparatus, acollection of a part of said prepaid credit, and apparatus operatinganomalies, and a second equipment interconnected across the telephoneline between said apparatus and said central office and detecting saidsignals transmitted by the first equipment and signals transmitted bythe central office to check particularly the operation of the apparatusand to establish, break and interrupt phases of a telephonecommunication.

The second active equipment is preferably installed close to thetelephone central office, and analyzes and manages the outgoing andincoming telephone communications. Such an equipment location improvessecurity, reliability and management of the public telephone apparatus.

According to a feature of the invention, the telephone line between thefirst and second equipments is energized with dc voltage from the secondequipment so that the latter can check the power supply to the firstequipment. This check is performed by monitoring a standby signal whichis transmitted permanently by the first equipment.

According to the invention, the first and second equipments areinteractive through signals exchanged only between the equipments, whichprovides constant, detailed monitoring of each phase of a communication.A self-surveillance thus provided by a looped, interactive signallingmakes the system more fraud-resistent, and technically the operation ofthe system is more reliable in the face of incidents of all types.Furthermore, all incidents are signalled and identified immediately.This procedure does away with all preventive maintenance.

In addition, the means for establishing, holding, breaking orinterrupting a communication included in the second equipment are thusout of reach of the public, which to a large extent guarantees correctoperation of the system. Thus, the second equipment is protected fromvandalism and the first equipment, installed on the public highway, iskept to the strict minimum.

According to features of the invention, the system allows mixedprepayment: coins and prepaid card. The management of a communication inthe second equipment is fully independent of coin and card collectingmechanisms included in the apparatus. Adaptation to the mechanisms takesplace at the level of a switching interface in the first equipment.During one same communication, the payment mode, coin or card, may atany moment be changed by the user. Thus a communication may be continuedwith coins when the card runs out of credits. In addition, mixedprepayment reduces the coin collection workload. For the user, a prepaidcard is easier to use than loose change, which also limits the user'stelephone consumption according to the number of coins in hispossession.

An actual collection of coins is checked in the first equipment bydetecting coins in at least three points along the coin chute into acoin box. A logic circuit in the first equipment detects any anomaly inthe coin flow direction, due to fraud with a "piece of string" orfraudulent access to a collection chute subjacent to the coin box forexample. In this case, an anomaly is recorded in less than one second inthe second equipment, as with coin box break-in, followed by remotecontrolled switching off.

According to other features, the second equipment monitors the openingof a compartment containing the coin box and/or removal of the coin box.Each opening of the coin box compartment automatically implies aregistration of an amount of coins contained in the coin box and anumber of charge unities cancelled from prepaid cards duringcommunications. These informations are instantly transmitted by thesecond equipment to a remote management means, such as a managementcomputer, in the same way as other operating anomaly signallings.

The second equipment restores the apparatus to the state awaitingcommunication or an out-of-service mode, as applicable, following anincorrect utilization by the user or an operating fault in the firstequipment such as absence of transmission of certain signals or anabsence of signals transmitted by the central office.

According to another features, the apparatus may be called by any otherpublic or private telephone apparatus. In this case, a special call toneis transmitted by the second equipment to the calling part to inform himthat he is calling a public telephone.

Generally speaking, the system embodying the invention is alsodistinguished by its capacity for integrated computerized management.This management covers the technical aspects such as signalling,location of faults, preventive maintenance and self-checking of allphases of a communication, automatic switching over to out-of-servicemode and automatic or manual return to in-service state as chosen by themanager, as well as the financial aspects such as coin collection,collected amounts, absence of traffic, average revenue, etc.

BRIEF DESCRIPTION OF THE DRAWING

The foregoing and other features and advantages of the invention will beapparent from the following description of several preferred embodimentsof the invention with reference to the corresponding accompanyingdrawings in which:

FIGS. 1A and 1B are schematic block diagrams of a first equipmentincluded in a public telephone apparatus, an audio circuit of theapparatus being detailed in FIG. 1A;

FIGS. 2A, 2B and 2C show in detail a coin checking circuit associatedwith a coin collecting mechanism, as well as a switching circuit workingin conjunction with the coin collecting mechanism and a prepaid cardcollecting mechanism in the telephone apparatus;

FIG. 3 shows in detail a signalling encoding and transmission circuitand a collection order receiving and decoding circuit order forming aninterface between the first equipment and a telephone line serving theapparatus;

FIGS. 4A and 4B are a block-diagram of a second equipment located closeto a local central office for monitoring and controlling the firstequipment, means for interconnecting various circuits in the secondequipment to the telephone line being shown in detail, and means formanaging several second equipment items being shown schematically;

FIG. 5 shows in detail a signalling receiving and decoding circuit and acollection order encoding and transmitting circuit included in thesecond equipment on the first equipment side;

FIGS. 6A and 6B show in detail a telephone communication monitorincluded in the second equipment;

FIG. 7 shows in detail a charge pulse detecting circuit and a voltagereversal and break detecting circuit included in the second equipment onthe central office side;

FIG. 8 shows in detail a charging checking circuit included in thesecond equipment; and

FIGS. 9A and 9B show an anomaly and coinage totalizer amount andcancelled charge unity storing circuit included in the second equipment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1A, 1B, 4A and 4B, a control and surveillance systemessentially comprises a first equipment 1 included in a prepaymentpublic telephone apparatus and a second equipment 2 located close to alocal central office and interconnected in a two-wire telephone lineAB-A₂ B₂ connecting the apparatus to the central office. Indeed, as willbe seen later, the telephone line A₀ B₀ -A₂ B₂ is a true telephone linebetween the second equipment and the central office conventionallycarrying voice signals and other known signals normally exchangedbetween a telephone set and a local central office. However, thetelephone line between the telephone apparatus and the second equipmentis a two wire line AB-A₁ B₁ energized with dc voltage by the secondequipment, remote powering the first equipment, and only carrying thevoice signals and the signals exchanged between the two equipments. Inparticular, the line between the apparatus and the second equipment doesnot transmit charge pulses delivered from the central office and is notsubject to a reply and hook on by a called party, such as first andsecond reversals of the central office battery voltage. The secondequipment only allows bi-directional transmission of signals within atelephone frequency band, between the first equipment and the centraloffice.

The first equipment 1 is hereinafter referred to as "passive equipment"because its various functions are mainly dependent upon a check made inthe second equipment. Consequently, the second equipment 2 is referredto as "active equipment" since it establishes, monitors, checks andmanages the various phases of a telephone communication at the requestof the first equipment.

The passive equipment 1 is firstly described with reference to FIGS. 1to 3, anticipating the description of certain functions of activeequipment 2 for the purposes of clarity. The active equipment 2 is thendescribed with reference to FIGS. 4 to 9.

PASSIVE EQUIPMENT

With reference to FIGS. 1A and 1B, the passive equipment 1 comprises anaudio circuit 10 for transmitting and receiving telephone signals andpowering other circuits of the passive equipment, a dialling keyboardsuch as a keyboard CD coupled to a decimal code signalling device, or akeyboard CMF coupled to a multifrequency code signalling device,according to the capabilities of the central office, a coin collectingmechanism 11 associated with a closed compartment of coin box 110, acoin checking circuit 12 for detecting and validating coins to becollected, a prepaid card collecting mechanism 13, a switching circuit14 for selecting the means of payment, coin or card, chosen by the user,a signalling encoding and transmitting circuit 15 and a collection orderreceiving and decoding circuit 16.

The passive equipment 1 is connected to terminals A and B of thetwo-wire telephone line via a protection circuit PRO. The PRO circuitprotects the logic circuits included in equipment 1 against allovervoltages occuring on the line.

The audio circuit 10 shown in FIG. 1A comprises a telephone handset Cequipped with a trigger P and a "hands-free" used audio block comprisinga microphone M and a loudspeaker HP. The handset C is connected to atelephone column containing the rest of passive equipment 1 by means ofa conductor cord COR, while the microphone M and the loudspeaker HP areflush with a wall of the column.

Voice signals are transmitted from a microphone m of the handset C orfrom microphone M, and voice signals are received into an earpiece e ofthe handset or into loudspeaker HP via a differential transformer 101.Differential transformer 101 is interconnected to the telephone linethrough a band-pass filter 100 having a telephone frequency pass band of300 to 3400 Hz and through the protection device PRO, and to a linebalancing network 102 terminating the line. The differential transformer101 provides protection against acoustic feedback, so called Larseneffect, by splitting the bidirectional telephone line into a receptionchannel 101R and a transmission channel 101T. The reception channel 101Ris connected to the loudspeaker HP and the earpiece e via movablecontacts of two switches 101R₁ and 101R₂. The transmission channel 101Tis connected to microphone M and m via movable contacts of two otherswitches 101T₁ and 101T₂. In addition to four conductive wiresconnecting earpiece e and the microphone into stationary contacts of twopairs of switches 101R₁, 101R₂ and 101T₁, 101T₂ respectively, the cordCOR contains two conductive wires to power a relay 103 when trigger P ispressed. Activation of relay 103 modifies the state of switches 101R₁,101R₂, 101T₁ and 101T₂ which disconnect the loudspeaker HP and themicrophone M from transformer 101 in order to connect the earpiece e andthe microphone m of the handset C to the telephone line. When trigger Pis released, the loudspeaker HP and the microphone M are connected tothe telephone line. Loudspeaker HP may thus receive a call tone when thetelephone apparatus is called by a remote subscriber.

The passive equipment 1 also comprises a dialling keyboard having keyswhich are accessible through a perforated wall of the telephone column.The keys cannot be torn off or pressed in excessively. When the localcentral office is capable of receiving audiofrequency dialling signals,the dialling keyboard is the multifrequency keyboard CMF transmitting acombination of two voice frequencies from among seven for each digit,via a second transmission channel 101TN of the differential transformer101. The keyboard CMF also comprises contacts 101C interconnected in thefirst transmission channel 101T to disconnect microphones M and m fromthe telephone line and power a multifrequency generator in the keyboardCMF after insertion of a coin in the mechanism 11, or a card withcredits remaining, in the mechanism 13, for transmission ofmultifrequency dialling signals without disturbance of the microphonesignals when the CMF keyboard keys are pressed. When the local centraloffice is able to receive rotary pulse dialling signals, the keyboard isthe keyboard CD coupled to a decimal signalling device transmittingpulse streams equal in number to the dialled digits. As will be seenhereinafter, the pulses modulate a set of signalling frequencies.

As shown in FIG. 1A, the audio circuit 10 also comprises means fortaking the electric power needed by the circuits contained in thepassive equipment 1, using the dc voltage of 48 volts in the telephoneline AB. As will be seen subsequently, the passive equipment powersupply voltage is not subject to reversal of the exchange batteryvoltage. Terminals A and B are at 0 and -48 volts respectively,corresponding to the central battery voltage. However, in otherembodiments, the passive equipment may be remote supplied by the activeequipment at a voltage of 96 volts or other suitable voltage. The takingmeans essentially comprises a general power supply 104 suitablyregulated and protected in order to supply dc voltages of 0 V, ±6 V, -12V and -24 V particularly. The power supply 104 is connected to thetelephone line between filter 100 and protection circuit PRO, via apower supply bridge 105 protected by an assembly of choke coils andcapacitors 106, a full-wave rectifier 107 and a filter 108. These lattercircuits protect the power supply 104 against accidental permutation ofwires A and B of the line and therefore against a reversal of thepolarities of these wires.

The coin collecting mechanism 11 and the prepaid card collectingmechanism 13 do not fall within the subject of the invention and willnot be described in detail.

The coin collecting mechanism 11 is capable of accepting various kindsof coins. Hereinafter, it will be assumed that N=4 different types ofcoins, P₁ to P₄, can be accepted for collection; for example, the valuesof the coins are P₁ =1 FF, P₂ =2 FF, P₃ =5 FF and P₄ =10 FF (Frenchfranc). The mechanism 11 particularly comprises four slides respectivelyin which coins P₁ to P₄ slide downward between coin insertion slots andstorage areas, and a switching device beneath the storage areas todirect each coin to the coin box contained in compartment 110, via acollection chute or to a refund dish via a refund chute.

As shown in FIG. 2A, contacts 112₁ to 112₄ are controlled respectivelyby detectors included in the storage areas. Each contact 112₁ to 112₄ isclosed provided at least one coin is present in the corresponding slide.When a collection order transmitted by the active equipment 2 isreceived by the passive equipment 1 and indicates that the balance of acommunication is negative, as will be seen hereinafter, one of four timerelays 113₁ to 113₄ opens one of collection contacts 114₁ to 114₄ tosend the corresponding detected coin into the collection chute throughthe switching device. However, the switching device empties the contentof all the storage slides into the refund chute when a pushbutton 115 ispressed in, and cuts off the power supply of the passive equipment via arelay 116 in order to simulate hook-on by the calling user; the userthen recuperates the coins which were stored pending collection.Releasing of relay 116 is also produced when there is a short cut inpower supply 104 for time t₃ =6 s, in particular at the end of acommunication under the control of the active equipment when the calledparty has hung up or when the balance of the communication in progressis negative for a predetermined period of t₂₂ =13 s, as will be seenhereinafter.

When a coin is being collected, it passes successively through threecoin descent detectors 117₁ to 117₃ located at three different levelsand each delivering a pulse to a respective output 118₁ to 118₃ ofmechanism 11 after the coin has passed. These detectors help to validatethe collection of each coin to be collected in order to notify thecollection of said coin to the active equipment. However, as will beseen hereinafter, the passage of a coin to be collected along a routedifferent from normal descent between the switching device and the coinbox is signalled to the active equipment by means of an anomaly signal.

The detection and validation of coins to be collected are now describedin detail with reference to the operation of the coin checking circuit12. Circuit 12 comprises a coin detecting circuit 17 and a coinvalidating circuit 18 shown in FIG. 2B.

The coin detecting circuit 17 comprises an OR gate 170 having fourinputs connected to the coin presence contacts 112₁ to 112₄respectively. An output 12PP of the OR gate is at logic state "1" assoon as a coin P₁ to P₄ is present in one of the storage slides, whichis indicated by the closed state of at least one of contacts 112₁ to112₄. Terminal 12PP at state "1" signals hook-off by the calling user.

Three AND gates 171₂, 171₃ and 171₄ allow collection of the coins in anorder of priority, starting with the coins having the lowest value P₁.This reduces the loss incurred by the user in the event of a diallingerror or a very short communication. Gates 171₂, 171₃ and 171₄ have two,three and four inputs respectively. Contact 112₁ is connected to firstinputs of the three gates 171₂ to 171₄ through an inverter 173₁. Contact112₂ is connected directly to a second input of gate 171₂, and via aninverter 173₂ to second inputs of gates 171₃ and 171₄. Contact 112₃ isconnected directly and via an inverter 173₃ to third inputs of gates171₃ and 171₄ respectively. Contact 112₄ is directly connected to afourth input of gate 171₄. Inputs S₁ to S₄ of flip-flops 174₁ to 174₄are connected to contact 112₁ and outputs of AND gates 171₂ to 171₄respectively. Thus input S_(n), n varying from 1 to N=4, is at state "1"and the other inputs S₁ to S_(n-1) and S_(n+1) to S_(N) are at "0"provided that one coin P_(n) is present in the corresponding slide andthat no coins of values less than P₁ to P_(n-1) are present in thecorresponding slides. As soon as a coin collection order is detected byreceiving circuit 16 and provided a card is not inserted in mechanism13, an output 160 of circuit 16 passes to state "1" and applies a "0" toinputs R of flips-flops 174₁ to 174₄ via an AND gate 140P in theswitching circuit 14 (FIG. 2C) and an inverser 175. Only flip-flop174_(n) corresponding to a coin with the lowest value among those coinspresent has an output Q at "1".

The outputs Q of flips-flops 174₁ to 174₄ are respectively connected tofirst inputs of AND gates 175₁ to 175₄ having second inputs connected tothe output 12E of gate 140P. Relays 113₁ to 113₄ are connected tooutputs of gates 175₁ to 175₄ via transistors 176₁ to 176₄ respectively.When the input S_(n) of flip-flop 174_(n) is at "1", gate 175_(n) isopened by the collection order signal and transistor 176_(n) is turnedon to activate relay 113_(n) (FIG. 2A). The activated relay 113_(n)opens the corresponding contact 114_(n) in order to neutralize coindetection during validation of collection of coin P_(n), and to signalthe presence of coin P_(n) by a "coin presence" pulse. As shown in FIG.2C, this pulse is delivered by output 12PP to an output 14P/C of theswitching circuit 14 via an AND gate 141₀ and an OR gate 142 in theswitching circuit 14. Activated relay 113 also controls the switchingdevice so that the coin P_(n) falls into the collection chute.

Normal descent of the coin P_(n) from top to bottom and its comingthrough the three stacked detectors 117₁, 117₂ and 117₃ in turn in thecollection chute is signalled by the coin validating circuit 18. Circuit18 shown in FIG. 2B comprises three RS flip-flops 180₁ to 180₃, twofour-input AND gates 181 and 182, one two-input AND gate 183, onetwo-input OR gate 184 and inverters 185₁ to 185₃, 186 and 187. Inputs Rof flip-flops 180₁ to 180₃ are connected to output 160 of the receivingcircuit via inverter 186. A collection order resets to "0" outputs Q offlips-flops 180₁ to 180₃ before collection proper of the coin P_(n) tobe collected. Inputs S of flips-flops 180₁ to 180₃ are connected tooutputs 118₁ to 118₃ of mechanism 11 respectively and are at "1" inresponse to coin P_(n) passing before detectors 117₁ to 117₃. Given thatthe output Q of flip-flop 180₃ is connected to the input S of flip-flop180₂ via inverser 187, the outputs Q of flips-flops 180₁ to 180₃ are at"1", "0" and "1" respectively when the coin P_(n) passes throughdetectors 117₁ to 117₃. The inputs of validation gate 181 are connecteddirectly to the collection order terminal 160 and to the outputs Q offlips-flops 180₁ and 180₃, and via inverter 185₂, to the output Q offlip-flop 180₂ respectively; an output 188 of gate 181 then passes to"1". This state validates collection of the coin by opening AND gates189₁ to 189₄ having other inputs connected to the outputs of gates 175₁to 175₄ respectively. In the switching circuit 14 shown in FIG. 2C, ANDgates 141₁ to 141₄ have first inputs connected to outputs 12P₁ to 12P₄of gates 189₁ to 189₄ respectively. Second control inputs of gates 141₀to 141₄ are at "1" and open these gates provided no card is present inmechanism 13. Then, among outputs 14P/C and 14P₁ to 14P₄ of gates 142and 141₁ to 141₄, only gate 14P_(n) is at "1" to indicate actualcollection of coin P_(n). The output 14P/C is at "0" if the coin justcollected was the last in the storage areas, or to "1" if one or morecoins are still waiting in the storage areas.

However, any abnormal combination of states of outputs Q of flips-flops180₁ to 180₃ other than "1", "0" and "1" keeps gates 181 and 189₁ to189₄ closed, and this abnormal combination is signalled by means ofgates 182, 183 and 184, with "1" on output 12A of circuit 12 connectedto the output of OR gate 184 via a diode 1840. In fact, the inputs ofthe AND gate 182 are connected directly to the output Q of flip-flop180₂ and terminal 160 and, via inverters 185₁ and 185₃, to the outputs Qof flips-flops 180₁ and 180₃ respectively; the inputs of the AND gate183 are connected to the outputs Q of flips-flops 180₁ and 180₃respectively; and the outputs of gates 182 and 183 are connected to theinputs of the OR gate 184 respectively. A "1" state at output 12Asignals an anomaly, for example resulting from extraction of a coin fromthe coin box in an upwards direction through detectors 117₃, 117₂ and117₁, or stoppage of the coin P_(n) to be collected before it reachesdetector 117₃ or at the level of detector 117₃, preceding aninterruption of the collection order signal, or following it, that is,whatever the state of terminal 160.

The prepaid card collection mechanism 13 shown in FIG. 2A also has twooutputs 13PC and 13TB and one input 13E acting similarly to output 12PP,outputs 12P₁ to 12P₄ and input 12E of the coin collection checkingcircuit 12, respectively. Output 13PC is at "1" when a card is presentin the mechanism 13 and has a positive charge unity credits remaining.In all other cases, such as absence of card, incorrect card, cardexhausted, or closure of card insertion slot in the mechanism 13, output13PC is at "0". In the switching circuit 14 shown in FIG. 2C, the output13PC is connected to control inputs of gates 140C and 140P directly andvia an inverter 143, to a second input of OR gate 142 and, via aninverser 144, to the control inputs of AND gates 141₀ to 141₄. AND gates140P and 140C have second inputs connected to terminal 160 and haveoutputs connected to terminals 12E and 13E respectively. Thus, if thereis no card, gates 140P and 141₀ to 141₄ are opened and the mechanism 11can be used for collection of coins and therefore enable thecommunication to be paid for with coins. However, if a card withremaining credits is present, only mechanism 13 can be used to pay forthe telephone communication, mechanism 13 receiving the order to collectthrough open gate 140C. A state "1" at the output 14P/C of OR gate 142indicates that either there is at least one coin present in the storageslides of mechanism 11, or that there is a card present in mechanism 13.Withdrawal or insertion of the card by the user, or the utilization ofall the credits on the card, does not interrupt the communication, andthe switching circuit 14 automatically substitutes mechanism 11 formechanism 13, and vice-versa. As regards the active equipment, thecommunication remains established and it must remain so whichever ofmechanisms 11 or 13 is in operation. In particular, the user with nocredits left on his card may continue the communication in progresswithout interruption, by inserting coins. The switching over betweenmechanisms 11 and 13 may be made at any moment without disturbing in theslightest either the communication or the charging.

The same pushbutton 115 is used simultaneously in the coin and cardcollecting mechanisms to cease a communication and trigger refund ofcoins in storage, and/or an ejection of the card.

The operating sequences between the active and passive equipments aretherefore similar during utilization of a card or of coins. Only theinterpretation of the collection order at terminal 160 differs inmechanisms 11 and 13. In the card collection mechanism 13, a collectionorder received at input 13E triggers a cancellation of a telephonecharge unity on the card. This cancellation is signalled by a state "1"at output 13TB, until the collection order signal is interrupted by theactive equipment when a charge unity credit register in the activeequipment is credited with the value of the cancelled charge unity andthus triggers a positive balance for the communication in progress, aswill be seen with reference to FIG. 8.

In order to avoid a distortion in the evaluation of the amount of thecoins contained in the coin box at the moment of its withdrawal, thedebited sums from cards are totalized in a charge unitytotalizer-counter distinct from a coinage totalizer-counter totalizingthe values of the collected coins. In addition, state "1" at output 13TBindicates to the active equipment that the card payment mode is used.

The different signals delivered from outputs 14P/C, 14P₁ to 14P₄, 12_(A)and 13TB are encoded and transmitted by the encoding and transmittingcircuit 15 shown in FIG. 3. Encoding consists in modulating combinationsof two frequencies selected from among five predetermined carrierfrequencies F₁ to F₅, by the pulses delivered from the abovementionedoutputs respectively. Circuit 15 comprises five oscillators 150₁ to 150₅producing the five carrier frequencies F₁ to F₅ respectively, as well asa gate circuit selecting the combinations of the two frequencies.Frequencies F₁ to F₅ have values higher than the telephone frequencyband of 300 to 3400 Hz and are, for example, F₁ =4800 Hz, F₂ =5600 Hz,F₃ =6400 Hz, F₄ =7200 Hz and F₅ =8000 Hz.

Outputs of a two-input NAND gate 151₁ and of four four-input OR gates151₂ to 151₅ are respectively connected to the mid-points of firstsecondary windings of double transformers included in symmetricalmodulators 152₁ to 152₅. First primary windings of the doubletransformers are connected to the outputs of oscillators 150₁ to 150₅.Second secondary windings forming outputs of modulators 151₂ to 151₅ areconnected in parallel to inputs of a bandpass filter 153 having apassband of 4000 to 8800 Hz, filter 153 being connected to terminals Aand B of the telephone line via a transformer 154 and protection circuitPRO. In each modulator 152₁ to 152₅, there are two forward-biased diodes155₁ to 155₅ between the first secondary winding and a second primarywinding of the associated double transformer. The transmissions offrequencies F₁ to F₅ from oscillators 150₁ to 150₅, which operatepermanently when power-supplied, are controlled by state "1" at theoutputs of gates 151₁ to 151₅ respectively, and the diode pairs 155₁ to155₅ are turned on respectively.

Frequency F₁ is not transmitted on the line when a collection order,reflected by state "1" at output 160 of the receiving circuit 16, isapplied to a first input of NAND gate 151₁ and when an absence of coinsfrom the storage slides and an absence of card with credits remainingare signalled by state "0" at terminal 14P/C which is connected to asecond input of gate 141₁ through an inverser 156. The output of NANDgate 151₁ is thus at state "0" and blocks diodes 155₁. Thus, afterestablishing a telephone communication, that is after hook-off,dialling, battery reversal reversing the polarity of the line wires onthe local central office side, and detection of the first charge pulseby the active equipment, frequency F₁, called as the standby frequency,is interrupted as soon as there are no more coins in the slides ofmechanism 11 and no card with credits remaining in mechanism 13, and assoon as a collection order is transmitted by the active equipmentresponsive to a negative balance for the communication in progress.However, the standby frequency F₁ is transmitted if at least one coin ispresent in the storage slides at the moment the collection order isreceived. After this collection, transmission of frequency F₁ ismaintained, despite the absence of coins in storage, until reception ofthe following collection order and provided that no coins have beeninserted in the meantime.

Outputs 14P₁ to 14P₄ of the switching circuit 14 are connected to inputsof gates 151₂ and 151₃, inputs of gates 151₂ and 151₄, inputs of gates151₂ and 151₅ and inputs of gates 151₃ and 151₄ respectively.Subsequently, effective collections of coins P₁, P₂, P₃ and P₄ aresignalled by combinations of carrier frequencies F₂ +F₃, F₂ +F₄, F₂ +F₅,and F₃ +F₄ respectively. Collection of a charge unity when a card ispresent, that is cancellation or debiting of one charge unity on thecard, results in application of a "1" to inputs of gates 151₄ and 151₅from output 13TB of mechanism 13, and therefore by transmission offrequencies F₄ +F₅.

In addition, two other frequency combinations may be transmitted bycircuit 15.

When the dialling phase uses a decimal keyboard, keyboard CD isactivated in response to hook-off simulated by the presence of a coin inthe storage slides or of a card in mechanism 13, reflected by a "1" atthe 14P/C output of the switching circuit. Dialling pulses are deliveredfrom an output IN of the keyboard CD to fourth inputs of OR gates 151₂to 152₅ via a two-input AND gate 157. As shown in FIG. 1B, output INreproduces the CD decimal keyboard dialling pulses provided that atransistor TR in the keyboard is turned on by a state "1" at terminal14P/C reflecting the presence of coins and/or card. The other input ofAND gate 157 is connected to an output Q of a RS flip-flop 158 viainverter 159. An input S of flip-flop 158 is connected to terminal 160of the receiving circuit, and an input R of flip-flop 158 is at state"0" by application of a biasing voltage of -6 volts. During thecommunication establishing phase until the first battery reversal,terminal 160 is at "0", which keeps gate 157 open. Each dialling pulsethus modulates a combination of carrier frequencies F₂ +F₃ +F₄ +F₅.Then, as soon as a collection order is received by circuit 16, flip-flop158 memorizes the "1" state and, via inverter 159, closes gate 157,which inhibits all transmission of dialling pulses from the terminal INof the keyboard CD. At the end of a telephone communication reflected bya brief interruption of the 48 V voltage on the line by the activeequipement, the input R of flip-flop 158 passes to "1", which againopens gate 157.

When a coin is not validated at collection, output 12A of validationcircuit 18 applies an "1" to inputs of gates 151₃ and 151₅, and acombination of frequencies F₃ +F₅ is transmitted to signal an anomaly.

The combination of frequencies F₃ +F₅ is also used to signal opening ofthe coin box compartment 110 and removal of the coin box fromcompartment 110. As shown in FIGS. 2 and 3, these two operationsrespectively open two contacts 117 and 118 series-connected between aterminal at +6 V and the common input 12A of OR gate 151₃ and 151₅. Asshown in more detail in FIG. 2A, terminal 12A is connected to terminal11R of mechanism 11 to which contacts 114₄ to 114₁ are series-connected,and to terminal 13R of mechanism 13. Opening of one of contacts 117 and118 thus cuts the 6 V power supply to mechanisms 11 and 13 and,consequently, terminals 14P/C, 14P₁ to 14P₄ and 13TB are kept at zero,which makes it impossible to establish a telephone communication.

As will be seen later on, the active equipment 2 sums the values of thecoins collected in the coin box as and when the communications takeplace, which means that the total amount collected since the last timethe coin box was emptied is known. This precise indication of the totalamount of the collections to date given by the active equipment, whichmanages the credit for each communication, also allows a check to bemade on the revenue collected by totalizing the values of the coinscollected independently of the reading of the telephone metersassociated with the public telephone apparatus. Given that the amountcontained in the coin box is known at the precise instant of coin boxwithdrawal, indicated by the opening of contacts 117 and 118, the designof the coin box is simple and it is no longer necessary to resort toinefficient and time-consuming sealing. The opening of contacts 117 and118 triggering transmission of frequencies F₃ +F₅ to the activeequipment triggers, in the active equipment, memorization of theextremely accurate total amount of the coins included in the coin boxand the number of charge unities provided from prepaid cards since theprevious withdrawal of the coin box. This memorization allows effectivechecking of the funds collected by the collection staff. During theperiod the coin box is being withdrawn, no telephone communication canbe established or held, since the active equipment simulates that theline is busy on the local central office side. If, at the beginning oftransmission of frequencies F₃ +F₅, corresponding to the opening ofcompartment 110, the latter contains a coin box and is then closedwithin a predetermined time of t₁ =130 s, the coin box withdrawal isconsidered to be normal. However, in all other cases, when the coin boxis absent and/or when the compartment is opened after time t₁, theactive equipment 2 places the public telephone in out-of-service mode bycutting the -48 V power supply to terminals AB of passive equipment 1.Outside, the coin box withdrawing periods preset by a managementcomputer, as will be seen later on, no time delay of t₁ =130 s takesplace. In normal operation, opening of the coin box compartment 110 byforce is signalled by transmission of frequencies F₃ +F₅ to the activeequipment which generates an alarm. Thus the presence and absence of the130 s time delay allows a differentiation to be made between thetransmissions of the F₃ +F₅ frequencies signalling incidents occuringafter normal withdrawing of the coin box and signalling break-in duringnormal operation.

As shown in FIG. 3, the receiving and decoding circuit 16 comprises abandpass filter 161 and a frequency detector 162. Filter 161 offers anarrow frequency-band centered on a carrier frequency F₆ =10000 Hzmodulated by collection order pulses. Inputs of filter 161 are connectedto the AB line terminals, between the protection circuit PRO and thefilter 100. This filter delivers F₆ frequency modulating pulses todetector 162 delivering each collection order in the form of a pulse onoutput 160. The duration of this pulse varies, but is generally equal toa maximum of t₂₁ =6 s.

As soon as the voice signal communication is established after the firstbattery reversal, the active equipment transmits through the line afirst collection order at frequency F₆ setting output 160 of thereceiving and decoding circuit 16 to "1". For this first collectionorder, a time delay t₅ =6 s is designated to remedy to an incidentconcerning collection of coin or cancellation of charge unity on a cardto avoid a blockage condition, as will be seen later on.

If, after a time not exceeding t₂₁, the active equipment receives anyone of the four combinations of frequencies F₂ +F₃, F₂ +F₄, F₂ +F₅ andF₃ +F₄ signalling that a coin is being collected normally, which isconfirmed by the absence of transmission of frequencies F₃ +F₅, andtherefore that the coin collecting mechanism 11 is used, the activeequipment 2 stops transmission of frequency F₆ and enters into a coinagecredit register for the communication, the value of the coincorresponding to the one of the five frequency combinations transmitted.Similarly, if after a time not exceeding t₂₁, the active equipmentreceives the combination F₄ +F₅, signalling cancellation of one chargeunity on a card and therefore use of prepaid card collecting mechanism13, the active equipment stops transmission of frequency F₆ and entersthe value of the charge unity for the communication into a charge unitycredit register. In both cases, the active equipment permanentlycompares the memorized credit with the status of the debit of thecommunication in progress, shown by the cost of charge unities or thenumber of charge unities respectively. Whenever the credit-debit balancebecomes negative, the active equipment delivers a collection ordercorresponding to frequency F₆. A new coin is collected, or a chargeunity is cancelled from the card, and the credit-debit balance becomespositive.

However, if during the time t₂₁ =6 s following transmission of eachcollection order at frequency F₆ after the first order, none of the fivecombinations of frequencies F₂ +F₃, F₂ +F₄, F₂ +F₅, F₃ +F₄ and F₄ +F₅ isreceived by the active equipment, which is also signalled byinterruption of the standby frequency F₁ indicating an absence of coinsin the storage slides, or an absence of card, or no credits remaining oncard present, the active equipment transmits to the audio circuit 10 a"no more credit" tone at 1250 Hz, which is superimposed on the voicesignals. This tone informs thus the user that he should feed at leastone coin into the mechanism 11 or insert a card with positive creditinto mechanism 13. Pending the credit input, the active equipmentsuspends the telephone communication between the public telephone andthe local central office and holds the 1250 Hz tone for a period of 7seconds following the t₂₁ =6 s time delay. However, the telephone linkis kept between the local central office and the remote user whoreceives a tone, preferably also at 1250 Hz, asking him to "pleasehold". After a time of t₂₂ =13 s succeeding the start of the tonetransmissions during which the balance remains negative, thecommunication is finally broken by the active equipment by means of abrief cut off of the power supply of the passive equipment.

ACTIVE EQUIPMENT

The active equipment 2 analyzes, monitors and manages the various phasesof a telephone communication. In particular, the active equipmentperforms detailed financial management of each communication, sums thecollection totals, making a distinction between a cash or coinageaccount and a prepaid-card charge-unity account, both for eachcommunication and globally for all communications since the lastwithdrawing of the coin box contained inside the public telephoneapparatus. Data collected by the active equipment are processed by aremote management computer OG which prints out the accounts situationand the quality of the operation of the passive equipment. In practice,several active equipments associated respectively with public telephoneapparatuses served by a common local central office are grouped togetherin an extensible frame able to contain up to 1024 active equipments. Asshown in FIG. 4B, all active equipments use a common link processor 3connected to the management computer OG via a modem 30 and a switchedtelephone line 31. The modem 30 operates in half-duplex, with amodulation rate generally of 200 bauds. The processor 3 is connected tothe modem through a signalling channel multiplexer-demultiplexer 32 andis also connected to a central memory 33, such as a wired memory or aREPROM. The memory 33 contains parameters subject to change, such as thevalue of the charge unity, a maximum cost of telephone communicationbeyond which the cost is considered to be abnormally high, a maximumnumber of charge unities which can be debited from a prepaid card, amaximum amount corresponding to a full coin box, and a telephone numberof the management computer OG.

With reference to FIGS. 4A and 4B, the active equipment 2 takes the formof a printed circuit board plugged into the above mentioned frame. Theactive equipment 2 is preferably located close to the local centraloffice of the public telephone apparatus. More exactly, the activeequipment comprises two terminals A₁ and B₁ connected to terminals A andB of the passive equipment 1 (FIG. 1B) via the telephone line properunder constant dc voltage, and two terminals A₀ and B₀ connected to thecorresponding terminals A₂ and B₂ of a corresponding junctor J0 of atelephone switchboard CT in the local central office via a distributionframe RE in the central office. As can be seen in FIGS. 4A and 4B, theactive equipment 2 also partly consists of a quadripole 20interconnected in the telephone line and comprising two voltage limiters200₁ and 200₀ across which various circuits included in the activeequipment 2 are connected in parallel. Voltage limiter 200₁ acrossterminals A₁ and B₁ protects the circuits against currents flowing inthe line between the active and the passive equipments, while voltagelimiter 200₀ across terminals A₀ and B₀ protects the circuits againstcurrents originating in the switchboard CT, such as an 80 V and 50 or 25Hz ringing current.

On the telephone line side, between terminals A₁ and B₁ and a filter 201having telephone passband of 300 to 3400 Hz, the active equipment 2comprises a receiving a decoding circuit 21 detecting the signallingcarrier frequencies F₁ to F₅ transmitted from the passive equipment 1,and an encoding and transmitting circuit 22 transmitting the signallingcarrier frequency F₆ to the passive equipment 1, as well as a doublesymmetrical transformer 202 constituting a telephone blocking circuit.On the passive equipment side, a first secondary winding of transformer202 is connected to terminals A₁ and B₁ to which circuits 21 and 22 areconnected in parallel, and comprises at its mid-point a capacitor 2030having terminals supplied at 0 V and -48 V through make contacts 2031and 2032 controlled by a relay 2033. Members 2030 to 2033 constitute apower supply bridge 203 for applying a -48 V dc voltage to the telephoneline and thus for remote supplying the passive equipment 1. Between asecond secondary winding and a first primary winding of the transformer202 are connected two blocking diodes 2020. When a nil voltage isapplied to a mid-point 2021 of the second secondary winding, the diodes2020 block bidirectional transmission of the audiofrequency voicesignals between the passive equipment 1 and the central office therebysuspending a communication between the user of the public telephoneapparatus and the remote subscriber. Blocking of diodes 2020 occurs whenthe balance of the communication in progress becomes negative for atleast t₂₁ =6 s.

Filter 201 is connected to a second primary winding of transformer 202on the passive equipment side, as well as to a secondary winding ofanother transformer 204 on the telephone central office side. In themiddle of a primary winding of transformer 204 is interconnected acapacitor 2050 connected in parallel with a series combination of aresistor 2051 and a contact 2052. Contact 2052 is controlled by a relay2053. Members 2051 to 2053 constitute a ringing and break circuit tosimulate, on the CT switchboard side, openings and closings of thetelephone loop during user hook-off, dialling with the decimal keyboardCD and user hook-off for an outgoing call. Between the primary windingof transformer 204 and voltage limiter 200₀, a voltage reversal andbreak detecting circuit 25 and a charge pulse detecting circuit 24 thatis connected to a charge checking circuit 26, are connected in parallelto terminals A₀ and B₀.

Circuit 25 detects three voltages applied by the switchboard acrossterminals A₀ and B₀. The first voltage corresponds to the rest status,outside the voice signal exchange phase of a telephone communication,and sets terminal A₀ and B₀ to -48 V and 0 V. A second voltage setsterminals A₀ and B₀ to 0 V and -48 V and corresponds to the voice signalexchange phase following the first reversal of the central batteryvoltage terminating the communication establishment phase. A thirdvoltage corresponds to a break in the -48 V power supply from theswitchboard CT, a break during which the switchboard CT transmits a callringing current of 80 V modulated at 50 or 25 Hz to terminals A₀ and B₀in order to call the public telephone apparatus and thus establish anincoming communication.

Circuit 24 detects 12 kHz charge pulses transmitted by a charging systemin the central office allocated to the public telephone apparatus, afterthe first reversal of the battery and during the voice phase. As isknown, the charging period between two charge pulses successivelytransmitted corresponds to a communication equal to the basic chargeunity and depends on the called party subscription area as indicated bya call number access code. The charging checking circuit 26 constantlycalculates the credit/debit balance for each communication and thusdetects any negative balance in order to interrupt the communicationeither briefly or definitively. Circuit 26 also establishes the totalsin coins and in basic charge unities since the last withdrawal of thecoin box contained in compartment 110 of the public telephone apparatus.

The quadripole 20 also comprises a transformer 206 between terminal B₁and the first secondary winding of double transformer 202 as well as atransformer 207 between the primary winding of transformer 204 andterminal B₀. Transformers 206 and 207 inject into the telephone line,and to the public telephone and the central office respectively, "nomore credit" and "please hold" tones as soon as the balance of thecommunication in progress becomes negative and no coin or card withcredit remaining is present in the passive equipment.

As can be seen in FIGS. 4A and 4B, the active equipment comprises, inaddition to circuits 20 to 26 already mentioned, a telephonecommunication monitor 27, a storing circuit 28 and a time base 29.Monitor 27 is the "brain" of active equipment 2 and is connected to allthe other circuits for centralization and analysis of all informationand for taking all appropriate decision, notably during the course of acommunication. Storing circuit 28 includes 32 memory blocks, eighteen ofwhich are intended to record anomalies indicated by the chargingchecking circuit 26 and the monitor 27 and twelve of which are intendedto record six digits giving the account of the coins and six digitsgiving the number of the charge unities delivered by the chargingchecking circuit 26 and totalized since the last coin box withdrawal. Infact, out of the eighteen memory blocks, eight memory blocks are usedhere, the others blocks remaining available for other uses not fallingwithin the scope of the invention.

As shown in FIG. 5, frequencies F₁ to F₅ are detected in the receivingand decoding circuit 21 via bandpass filters 211₁ to 211₅ connected inparallel to a wideband filter 210 of 4000 to 8800 Hz, and followed bytuned amplifiers 212₁ to 212₅ and full-wave rectifiers 213₁ to 213₅respectively. Inputs of filter 210 are connected to terminals A₁ and B₁of the telephone line on the passive equipment 1 side. Outputs 21V and214₂ to 214₅ of rectifiers 213₁ to 213₅ each delivers a dc voltage athigh level "1" when the respective frequency F₁ to F₅ is detected. A setof six three-input AND gates 215₁ to 215₆ and a four-input AND gate 215₇decodes all frequencies F₂ to F₅ to respectively signal collections ofcoins P₁ to P₄ to outputs 21P₁ to 21P₄, debiting of a charge unity froma prepaid card on output 21TB, an anomaly such as collection of aninvalid coin or opening of the coin box compartment and/or withdrawal ofthe coin box on output 21A, and a communication request or diallingpulses on output 21DEC. The signals at outputs 21P₁ to 21P₄, 21TB, 21Aand 21DEC are similar to those applied to terminals 14P₁ to 14P₄, 13TB,12A and to the output of gate 157 in the passive equipment (FIG. 3).Thus terminal 214₂ is connected to inputs of gates 215₁, 215₂ and 215₃,terminal 214₃ to inputs of gates 215₁, 215₄ and 215₆, terminal 214₄ toinputs of gates 215₂, 215₄, and 215₅, and terminal 215₅ to inputs ofgates 215₃, 215₅ and 215₆. The four inputs of gate 215₇ are connected toterminal 214₂ to 214₅ respectively.

Circuit 21 also comprises an OR gate 216 having four inputs connected toterminals 214₂ to 214₅, and a NOR gate 217 having two inputs connectedto terminal 21DEC and an output terminal 28ICT of storing circuit 28. Anoutput of gate 217 is connected to third inputs of AND gates 215₁ to215₆ in order to close these gates during reception of the combinationof frequencies F₂ to F₅ corresponding to the dialling phase using thekeyboard CD, or during transmission of the digits giving the totalamounts of coins and charge unities from the storing circuit 28 to themanagement computer OG in order to inhibit the counting functions in thecharging checking circuit. Capacitors 218₁ to 218₆ shunt connected atthe outputs of gates 215₁ to 215₆ respectively, delay the polarizationof respective output terminals 21P₁ to 21P₄, 21TB and 21A by a fewnanoseconds in order to take into account the opening time of AND gate215₇. An output 21P/C of OR gate 216 is connected to a trigger input D₁of a timer 271₁ in monitor 27 shown in FIG. 6A. As will be seen lateron, timer 271₁ derives a time delay t₁ =130 s to check the time taken toestablish a communication in response to the detection of one offrequencies F₂ to F₅. Thus, from the start of the communication, thecorrect operation of all the circuits monitoring signalling and chargingis checked. Indeed, as will be seen later, if one or more of frequenciesF₂ to F₅ is not received, the AND gate 215₇ does not control ringing andbreaking relay 2053 on the local switchboard CT side, while onlyreception of one of frequencies F₂ to F₅ opens OR gate 216 and triggerstime delay t₁ =130 s in timer 271₁ (FIG. 6A). After time delay t₁, andif no communication has been established, monitor 27 records a non-validcommunication and releases the charging system. Similarly, in the othertransmission direction, link between the calling and called parties isdependent on correct reception of a 12 kHz charge pulse from theswitchboard CT, the correct transmission and reception of frequency F₆and, in return, correct reception of one of signals indicating actualcollection.

The encoding and transmitting circuit 22 and the time base 29 are alsoshown in FIG. 5.

Circuit 22 comprises an oscillator 221 oscillating at frequency F₆=10000 Hz, a transistor 222 and a bandpass filter 223 having a narrowband centered on frequency F₆. An output 224 of oscillator 221 isconnected to an input of filter 223 via a collector-emitter junction oftransistor 222, as well as to inputs of two frequency dividers 291 and292 included in time base 29. A base 220E of transistor 222 receives acollection order pulse from the charging checking circuit 26 in order toturn on transistor 222 and transmit frequency F₆ on the telephone linethrough filter 223 connected to terminal A₁ and B₁ on the passiveequipment 1 side. Transistor 222 amplified the F₆ signal and matches theload at the output of oscillator 221.

Frequency dividers 291 and 292 are binary counters and divide frequencyF₆ =10000 Hz by 8 and 8192 respectively, in order to provide clocksignals to two clock inputs 27TON and 27H of monitor 27. The first clocksignal at terminal 27TON has a frequency of 1250 Hz for transmissionrespectively as "no more credit" and "please hold" tones to the callingparty passive equipment 1 and to the called party through theswitchboard CT in the local central office. The second clock signal atterminal 27H is delivered to clock terminals H₁ to H₃ and H₅ of timers271₁ to 271₃ in monitor 27 in order to determine various significanttimes during the course of a communication.

Before presenting the operation of monitor 27 shown in FIG. 6, a briefdescription of circuits 24 and 25 shown in FIG. 7 is given.

The charge pulse detecting circuit 24 comprises a bandpass filter 240centered on the 12 kHz modulation frequency of the charge pulsestransmitted by the charging system of switchboard CT and received viaterminals A₀ and B₀. A tuned circuit 241 and a full wave rectifier 242at the output of filter 240 amplify and demodulate the detected chargepulses which are then calibrated by a non retriggerable monostableflip-flop 243. An output 24IT of flip-flop 243 transmits the calibratedcharge pulses to the charging checking circuit 26.

The calibrated pulses have a width appreciably greater than that of thedetected pulses in order to cancel out the effects which could lead tocharging errors because of microbreaks affecting reception of the 12 kHzfrequency delivered from the switchboard CT. In addition, it is to benoted that, contrary to the majority of current public telephoneapparatuses, the charge pulses are not transmitted to the publictelephone apparatuses, since filter 201 (FIG. 4) does not allow such atransmission.

The voltage reversal and break detecting circuit 25 shown in FIG. 7comprises two networks each of which includes an inductor 25L₁, 25L₂, aresistor 25R₁, 25R₂ and a forward-biased diode 25D₁, 25D₂ connected inseries. Terminals of inductors 25L₁ and 25L₂ are connected to the lineterminals A₀ and B₀, and cathodes of diodes 25D₁ and 25D₂ are connectedto a common terminal 250. Terminal 250 is connected to a reset input RZof a timer 251 having an input H receiving the clock signal fromterminal 27H of time base 29 and establishing a duration of t_(AP) =20 sfor calling the public telephone apparatus. Terminal 250 is alsoconnected to an output terminal 25AP of circuit 25 via an inverter 252to signal to the monitor 27 a call from a remote party, and to a triggerinput D of timer 251 and an input S of a RS flip-flop 253. An input R offlip-flop 253 is connected to a terminal common to inductor 25L₂ andresistor 25R₂ via a monostable flip-flop 254 triggerable by fallingedge.

In addition, circuit 25 comprises two resistors 255 and 256 and aforward-biased diode 257 interconnected between a ground referencedterminal and a terminal common to inductor 25L₁ and resistor 25R₁. Aterminal common to resistors 255 and 256 is connected to a first inputof AND gate 258 having a second input connected to an output S of timer251 via an inverter 259. An output 25IB of gate 258 constitutes anoutput of circuit 25 for signalling battery reversal, and moreparticularly for signalling a voice signal exchange phase to the monitor27 and to the charging checking circuit 26.

Whatever the mode of power supply from the switchboard CT battery toline terminals A₀ and B₀, terminal 250 is always biased with -24 V,which signals line power supply on the switchboard side to monitor 27. Apower supply break in response to a call by a remote subscriber, as willbe seen later on, sets terminals 250 to state "0" and thus outputterminal 25AP to state "1".

When the line is at rest, outside a conversion phase, that is whenterminals A₀ and B₀ are at -48 V and 0 V, diodes 25D₁, 25D₂ and 257block all flowing of current. Seen from the switchboard, an end of thetelephone line relative to circuit 25 is "open". At this time, networks25L₁ to 25D₂ have no counteracting effect on any activation of theringing and breaking relay 2053. In the rest state, the first input ofAND gate 258 is biased with 0 V, corresponding to logic state "0".

After a first reversal of the battery voltage, indicating the start of aconversation phase in a telephone communication, terminals A₀ and B₀ areat 0 and -48 V, diode 257 conducts, and the first input of gate 258 isbiased with -6 V, corresponding to logic state "1". Resistors 25R₁, 255and 256 have resistances such that in no case subsequently networks 25L₁to 25D₂ neutralize activation of relay 2053 which has to signal the endof a communication to the switchboard CT by opening the line.

MONITOR

The structure and operation of monitor 27 is now described withreference to FIGS. 6A and 6B, together with the structure and operationof the charging checking circuit 26 shown in FIG. 8. Monitor 27 notablycomprises six timers 271₁ to 272₅ setting respective predetermined timedelays of t₁ =130 s; t₂₁ =6 s, t₂₂ =13 s and t₂₃ =26 s; t₃ =6 s; t₄ =102ms and t₅ =6 s, for determining various significant times during acommunication and thus checking the communication phases and signallinganomalies. At the end of the abovementioned respective time delays,outputs S₁ ; S₂₁, S₂₂, S₂₃ ; S₃, S₄ and S₅ pass to state "1". Each oftimers 271₁, 271₂, 271₃ and 271₅ is a flip-flop counter receiving aclock signal delivered from time base 29 (FIG. 5) at a respective inputH₁, H₂, H₃ and H₅, via terminal 27H. Timer 271₄ is also a flip-flopcounter receiving a 1250 Hz clock signal from time base 29 on input H₄,via terminal 27TON. Each timer 271₁ to 271₅ is triggered by a state "1"on respective input D₁ and D₅ and reset by a "1" on respective input RZ₁to RZ₅.

Various other logic members includes in the monitor 27 are cited duringthe following description of the various phases of an outgoingcommunication, a coin box withdrawal and an incoming communication.

(A) Rest phase

When the printing circuit board supporting active equipment 2 is pluggedin, a transistor 272₁ is turned on and activates power supply relay 2033via monitor output 27AL. Contacts 2031 and 2032 in the power supplybridge 203 are closed to supply the passive equipment 1 with 48 Vthrough terminals A₁ -B₁ and A-B of the telephone line. Simultaneously,the failure to receive frequency F₁ during startup of passive equipment1 holds output terminal 21V of the receiving circuit 21 at state "0",which triggers timer 271₂ via inverter 273₁. It is recalled that timer271₂ sets three time delays t₂₁, t₂₂ and t₂₃ equal to 6, 13 and 26seconds respectively, at expiry of which outputs S₂₁, S₂₂ and S₂₃ are atstate "1". Then, very quickly, the general power supply 104 in thepassive equipment 1 powers all the circuits in it, and standby frequencyF₁ is transmitted normally to the active equipment well before the endof time delay t₂₃ =26 s. Terminal 21V connected to a reset terminal RZ₂of timer 271₂ is then at "1" and resets timer 271₂. The passiveequipment is then ready to establish a communication and the activeequipment is ready to monitor said communication.

Failure to receive frequency F₁ after t₂₃ =26 s following powering ofthe telephone line, sets to "1" an anomaly input 28A₁ of the storingcircuit 28 via AND gate 274₁ having two inputs connected to output S₂₃of timer 271₂, and to the output of inverter 273₁ and input D₂ of timer271₂. The output of gate 274₁ is also connected to a base of transistor272₁ through an inverter 273₂ and turns off transistor 272₁ which stopsthe power supply to the passive equipment and places it inout-of-service mode. Output 28A₁ thus indicates a passive equipmentpower supply failure due for example to a failure in the F₁ frequencytransmitting and receiving means including notably circuits 150₁, 152₁,211₁ and 213₁ (FIGS. 3 and 5), or an abnormal attenuation, or line cutbetween terminals A, B and A₁, B₁. This anomaly is signalled to themanagement computer OG. After repair, the passive equipment isautomatically restarted by the active equipment as soon as frequency F₁is received.

(B) Hook-off phase

In passive equipment 1, insertion of a prepaid card with remainingcredits into mechanism 13 or insertion of at least one coin intomechanism 11 sets the output 14P/C of the switching circuit 14 (FIG. 2C)to "1", which simulates calling party hook-off by opening AND gate 157(FIG. 3) triggering transmission of frequencies F₂ to F₅ to the activeequipment. Output 21DEC of the receiving circuit 21 passes to state "1"and turns on a transistor 272₂ through a diode 275₁. The collector oftransistor 272₂ activates, via an output terminal 27AC, the ringing andbreaking relay 2053 which closes contact 2052. The telephone line on theswitchboard side is looped, which simulates hook-off as in aconventional telephone set with a hook proper. If one of frequencies F₂to F₅ is not received in circuit 21, no hook-off operation is detectedby the switchboard CT, gate 215₇ remaining closed. However, reception ofany one of the four frequencies F₂ to F₅ is sufficient to set output21P/C of OR gate 216 in circuit 21 to "1" and trigger timer 271₁.

In all the abovementioned cases, the timer 271₁ sets a time delay of t₁=130 s which is allocated for dialling, ringing, called party reply andreception of a first collection order at frequency F₆ by passiveequipment 1 which follows the first charge pulse transmitted from theswitchboard CT to the active equipment 2. At the end of the time delayt₁ =130 s, output S₁ of timer 271₁ passes from "0" to "1", whichtriggers timer 271₃ through a four-input OR gate 276₁. Output S₃ oftimer 271₃ connected to output RZ₃ thereof then turns off transistor272₁ through a diode 275₁ for a time t₃ =6 s. The power supply of thepassive equipment 1 is then cut off for time t₃ by deactivation of relay2033. Such a power supply break triggers refunding of coins stillpresent in the storage slides of mechanism 11 and/or ejection of thecard from mechanism 13, at the end of a telephone communication.

In addition, at the end of time delay t₁ =130 s, output S₁ of timer 271₁sets inputs of three two-input AND gates 274₂ to 274₄, to "1". Otherinputs to gates 274₂ to 274₄ are connected respectively to output 21DECof receiving circuit 21 directly and via an inverter 273₃. Thus, if atleast one of frequencies F₂ to F₅ is not received after t₁ =130 sfollowing the hook-off phase indicated by transmission of at least onefrequencies F₂ to F₅, an anomaly input 28A₂ of storage circuit 28connected to the output of AND gate 274₃ passes to "1". This indicatesan anomaly in the operation of the passive equipment or the activeequipment, such as failure of one of the means for transmitting orreceiving one or more frequencies F₂ to F₅, or an abnormal attenuationof the line across terminals AB and A₁ B₁.

In a normal case in which all frequencies F₂ to F₅ are received at theend of time delay t₁ =130 s, the end of the communication is marked, asalready stated, by a brief break in the power supply of the passiveequipment for time t₃ =6 s and terminal 28A₁ stays at "0". In this case,a clock input H₇ of a counter 277 connected to an output of AND gate274₂ passes to "1" and increments the counter 277 by one unity. A resetinput RZ₇ of counter 277 is connected to a battery reversal output 25IBof circuit 25 and resets counter 277 in response to each batteryreversal originating from switchboard CT corresponding to hook-off bythe called party. Counter 277 comprises three binary stages and has anoutput S₇ constituting a third anomaly input 28A₃ of storing circuit 28connected to the base of transistor 272₁ via an inverter 273₇. Thus,when at least eight consecutive call attempts fail, chiefly due to adialling incident on the keyboard CD or other incident duringestablishment of the communication, such as absence of charge pulse orfailure of switchboard CT, the count of counter 277 remains blocked ateight and the passive equipment is placed in out-of-service mode byblocking transistor 272₁ and deactivating power supply relay 2033.

In this latter case, restoration of the power supply of passiveequipment 1 and resetting of counter 277 are manually controlled by anoperator using the management computer OG, this computer having receivedthe anomaly signalling through terminal 29A₃, as will be seenhereinafter. The operator enters on the computer OG keyboard the addressof active equipment 2 and a "restore" code which is transmitted tostoring circuit 28 and results in a "1" at output 28R of circuit 28.Output 28R is connected to the base of transistor 272₁ through aninverter 273₅ and to input RZ₁ of counter 277 through a monostableflip-flop 278₁. In this case, triggering of flip-flop 278₁ by a risingedge resets counter 277 whose output S₇ turns on transistor 272₁ toagain power passive equipment 1.

(C) Dialling and selection

The detection of four frequencies F₂ to F₅, reflected by a "1" atterminal 21DEC, following insertion of a coin or a card, closes theringing and break contact 2052, as already stated. In response to this"hook-off" operation, the switchboard CT transmits the dialling tone topassive equipment 1.

When the multifrequency keyboard CMF is used, the multifrequencydialling signals pass directly through the quadripole 20 withoutintervention by the other active equipment circuits.

When the decimal keyboard CD is used, dialling pulses of 77 ms modulatethe combination of frequencies F₂ to F₅. The pulses and breaks betweenthese pulses alternately turn on and turn off transistor 272₂ and arerepeated towards telephone switchboard CT by closings and openings ofthe ringing and break contact 2052 and thus loopings and unloopings ofthe line. Staccato triggering of timer 271₁ will only cease whentransmission of frequencies F₂ to F₅ is stopped normally by the passiveequipment in response to the first collection order pulse modulatingfrequency F₆, this stoppage being effected by flip-flop 158 (FIG. 3).Breaks of 33 ms between the dialling pulses do not permit stoppage ofthe time delay sequence t₁ =130 seconds. Timer 272₁ will only be stoppedby an interrupt greater than 102 ms in the dialling stream F₂ to F₅ inorder to discount the 33 ms dialling pauses during the 130 second total.This result is obtained by means of timer 271₄ with delay t₄ =102 mswhich is triggered by breaks in frequencies F₂ to F₅ via terminal 21DEC,an inverter 273₆ and its input D₄, which is reset by re-establishment offrequencies F₂ to F₅ via terminal 21DEC and its input RZ₄ and finallywhich controls after 102 ms, via its output S₄, a two-input OR gate 276₂and its input RZ₁, stoppage and resetting of timer 271₁. It is recalledthat the 130 seconds correspond to a maximum time lapse between themoment the user "hooks off" and the moment he enters contact with hiscorrespondent. It should be stated that timer 271₁ is not retriggered bydialling breaks received at input D₁.

If the calling user does not press the refund button 115 (FIG. 2A), adialling incident, a called party line busy, a called party hook-offfault, or a charging failure in switchboard CT leads to the situationalready described, that is expiry of time delay t₁ =130 s, release ofthe telephone line, refund of coin or ejection of card by cutting thepower supply for time t₃ =6 s and incrementation of counter 277 by oneunity.

(D) Called party reply

Hook-off by the called party results in a first reversal of the batteryand setting of the line terminals A₀ and B₀ on the switchboard CT sideto 0 and -48 V. This first battery reversal results in a "1" at output25IB of voltage reversal and break detecting circuit 25 (FIG. 7).Terminal 25IB is connected to the base of transistor 272₂ via a diode275₃ and thus confirms conducting condition of transistor 275₂.Activation of relay 2053 is thus ensured when transmission offrequencies F₂ to F₅ ceases and terminal 21DEC returns to "0", afterreception of the first collection order by the passive equipment anduntil the end of the communication. Thus, first battery reversal takesplace before the break in frequencies F₂ to F₅.

As already stated, the first battery reversal resets counter 277. Thishas no effect on timer 271₃ intended for a power supply cut to thepassive equipment, by means of a monostable flip-flop 278₂ triggerableby falling edges and thus in response to a second battery reversalsignalling the end of the communication. The flip-flop 278₂ has an inputconnected to terminal 25IB and an output connected to input D₃ of timer271₃ via OR gate 276₁. In addition, the first battery reversal isaccompanied by a first 12 kHz charge pulse transmitted by theswitchboard CT and detected by detecting circuit 24 whose output 24ITtransmits a calibrated charge pulse.

With reference to the charging checking circuit 26 shown in FIG. 8,terminal 24IT is connected to control inputs of 12 AND gates 260₁ to260₁₂, and to a clock input of a card charge unity debit register 26DTB.Other inputs of AND gates 260₁ to 260₁₂ are connected through atwelve-wire bus 33TB to the central memory 33 which delivers thethree-digit cost of a basic charge unity in centimes, each digit beingencoded by a 4-bit word. Outputs of gates 260₁ to 260₁₂ are connected totwelve inputs of the coinage debit register 26DM. Thus, in response to acalibrated charge pulse at terminal 24IT, the register 26DM isincremented by the cost of a basic charge unity, and register 26DTB isincremented by one unity. The counts in registers 26DM and 26DTB areconstantly compared with the counts in a coinage credit register 26CRMand a card charge unity credit register 26CRTB by means of a coinagecomparator 26CM and a basic charge unity comparator 26CTB respectively.Register 26CRM has inputs connected to outputs 21P₁ to 21P₄ of receivingcircuit 21, and add the value of a coin collected to the coinage creditcount whenever the corresponding terminal 21P₁ to 21P₄ passes to"1".Similarly, register 26CRTB is connected to output 21TB of receivingcircuit 21 and is incremented by one unity in response to a "1" atoutput 21TB corresponding to cancellation of a basic charge unity in aprepaid card. An output of comparator 26CM passes to "1" whenever thecoinage balance equal to the difference between the counts in the tworegisters 26CRM and 26DM is negative. An output of comparator 26CTBpasses to "1" whenever the basic charge unity balance equal to thedifference between the counts in registers 26CRTB and 26DTB is negative.

The four registers 26DM, 26DTB, 26CRM and 26CRTB are intended formanagement of a single telephone communication and are reset to zero byrising and falling edges on terminal 25IB corresponding to the first andsecond battery reversals marking the limits of the conversation phase.This reset is obtained by means of an inverter 261 interconnected toterminal 25IB and reset inputs RZ of registers 26DM, 26DTB, 26CRM and26CRTB via diodes 262 respectively.

In response to the first charge pulse following the first batteryreversal, the coinage and charge unity balances derived by comparators26CM and 26CTB become negative, which triggers transmission of acollection order at frequency F₆. For this purpose, outputs ofcomparators 26CM and 26CTB are connected to two inputs of an AND gate263 having another input connected to terminal 25IB and having an outputconnected to input 220E of transmitting circuit 22. Thanks to gate 263,no collection order can be transmitted before hook-off by the calledsubscriber as signalled by the first battery reversal.

(E) Credit exhausted

(E1) When at least one coin is present in the storage slides ofmechanism 11, the coin having the lowest value is collected in responseto the first collection order, which increments the coinage creditregister 26CRM by the value of the collected coin. For a basic chargecost of for example 0,75 FF, as is the case at present in France, andaccording to the value of the last coin inserted or collected before theend of the communication, apart from duration t₂₁ =6 s granted forinsertion of a coin with risk of reception of "no more credit" tone, theuser has a free communication period corresponding to a cost of(2×0.75)-1=0.50 FF for a coin P₁ =1 FF, of (3×0.75)-2=0.25 FF for a coinP₂ =2 FF, of (7=0.75)-5=0.25 FF for a coin P₄ =5 FF and of(14×0.75)-10=0.50 FF for a coin P₄ =10 FF. However, a loss of thisnature is of little significance for the authorities since it iscompensated by a minimum collection of 1 FF at the beginning ofcommunication and by credits remaining available at the end of thecommunication. This particularity, which corresponds to charging markedat the end of the period due, has an inverse effect and works to theadvantage of the utility if the charging precedes the period due. Thissituation is not applicable to this system alone and currently exists inthe system in service. It is the result of simple chance that the basiccharge unity is a common divider of the values of the various coins inuse. Only the prepaid card allows a more accurate payment mode.

In response to the first validated and collected coin, register 26CRM isincremented by the value of this coin, the coinage balance then becomespositive and the output of comparator 26CM passes to "0" to close ANDgate 263, which stops transmission of frequency F₆. Similarly, if aprepaid card is present in mechanism 13, reception of frequency R₆ inthe passive equipment results in the transmission of a pulse signifyingcancellation of a basic charge unity from the card and setting ofterminal 21TB to "1", which credits register 26CRTB with one unity andstops transmission of freqnency F₆. Thus, as soon as one of comparators26CM and 26CTB detects a positive balance, the transmission of frequencyF₆ is stopped, and will again be triggered as soon as the two outputs ofcomparators 26CM and 26CTB are again at "1", i.e. in response to passageof the two coinage and charge unity balances from positive or nil tonegative.

It is recalled that when coins are present in the storage slides ofmechanism 11 or a prepaid card having credits remaining is inserted inmechanism 13, the collection order signalled by frequency F₆ istransmitted to the passive equipment as soon as comparators 26CM and26CTB detect a negative balance. The received collection order triggersnormally activation of one of relays 113₁ to 113₄ through switchingcircuit 14 (FIG. 2) to collect a coin, or set input 13E to "1" to cancela charge unity in the card. This operation is indicated by setting to"1" of one of terminals 14P₁ to 14P₄ or of terminal 13TB.

If for any reason a coin is not collected, due for example to a faultycorresponding relay 113₁ to 113₄, or if a charge unity is not cancelledin a card, the balance remains negative, the frequencies F₁ to F₆ aretransmitted and the timer 271₂ is not triggered. In this case, allterminals 21P₁ to 21P₄ and 21TB remain at "0" and the communication maybe continued free of charge. To remedy this situation, monitor 27comprises an AND gate 274₅ having two inputs connected to terminal 21Vand to the output of gate 263, and having an output connected via aninverter 273₆ to reset terminal RZ₅ and directly to trigger terminal D₅of timer 271₅. Output S₅ of timer 271₅ is connected to input D₃ of timer271₃ via OR gate 276₁ and to an anomaly input 28A₄ of storing circuit28.

As soon as the collection order is transmitted by gate 263 to thepassive equipment, gate 274₅ triggers timer 271₅, frequency F₁ normallybeing transmitted when there is still a coin or card with remainingcredit in the passive equipment. If, before the end of time delay t₅ =6s established by timer 271₅, one of terminals 21P₁ to 21P₄ and 21TB isgone to "1", one of the two balances is again positive and thetransmission of frequency F₆ stops, timer 271₅ returning to "0" untilthe next collection order. The communication is then continued untilthere are no more coins or credits on the card or until the calling orcalled party hangs up. During the communication, a comparator 26MMAX incircuit 26 shown in FIG. 8, constantly compares the coinage creditoutputting from register 26CRM with the maximum cost of a communicationdelivered from output bus 33CM from the central memory (FIG. 4B). When acommunication is abnormally long, an output of comparator 26MMAX sets ananomaly input 28A.sub. 5 of storing circuit 28 to "1". Similarly, duringthe communication, a comparator 26TBMAX included in circuit 26constantly compares the charge unity credit outputting from register26CRTB with the maximum number of basic charge unities in a prepaidcard, delivered from output bus 33TBM from memory 33. An output ofcomparator 26TBMAX sets an anomaly input 28A₆ of storing circuit 28 to"1" when the communication using the card is abnormally long. In boththese cases, the "excessively long communication" anomaly is transmittedfor information to the management computer OG.

However, if the balance is still negative and the collection order isagain transmitted after time delay t₅ =6 s, output S₅ of timer 271₅passes to "1" and triggers timer 271₃ and thus the break in the powersupply of the passive equipment and the end of the communication, withrefund of the coin or ejection of the card. In addition, terminal 28A₄is at "1", which signals an anomaly written in storing circuit 28. Thisanomaly is transmitted to the management computer OG via processor 3which, in return, receives an acknowledgement signal. It is to be notedthat the failure to place the passive equipment in out-of-service modefor this type of anomaly is intentional. Indeed, this anomaly is aresult of:

either a technical failure which has just occured, in which case, thefollowing communication(s) will give rise to characterized anomaliessignalled by other anomaly inputs 28A₁ to 28A₃ and 28A₈ for example,

or a stockage slide blocking in the switching device of mechanism 11,the end of the communication and the refund being adapted to find againa normal operation condition,

or a fraudulent action, the thwarting of this attempt by breaking thecommunication seems to be sufficient and does not warrant placing thepassive equipment in out-of-service mode.

Several anomalies indicated to the management computer by termial 28A₄lead in principle to a series of fruitless call attempts, similar to theanomalies signalled at terminal 28A₃, and require a check of the correctoperation of the coin collecting mechanism 11 with regard to the slidesand the level detectors 117₁ to 117₃ and the correct operation of thecard collecting mechanism 13 with regard to the prepaid card cancellingand checking circuit.

In addition, as already stated, a charge pulse delivered from theswitchboard CT simultaneously increments the coinage debit register 26DMwith a cost in centimes of a basic charge unity and the charge unitydebit register 26DTB with a charging unity. When both coinage and chargeunity balances are negative for a conversation phase established afterfirst battery reversal, this causes the transmission of the collectionorder to the passive equipment, via AND gate 263.

If the collection is in coinage, one of terminals 21P₁ to 21P₄ creditsthe count of register 26CRM with an amount equal to the value of thecollected coin. In addition, one of terminals 21P₁ to 21P₄, via OR gate264 and diode 265, resets the charge unity debit and credit registers26DTB and 26CRTB. The balance in "cash" is then positive and the balancein charge unities is nil, which stops transmission of the collectionorder. However, at the moment the collection order is sent, the balancein charge unities is negative by one unity and the balance in coinage isnegative by an amount less than the cost of a charge unity.

Instead of continuing payment in coinage, the user changes the paymentmode and uses a prepaid card. Verification tests are performed by thecard collecting mechanism 13. Mechanisms 11 and 13 are switched inswitching circuit 13 in the passive equipment, and a basic charge unityis cancelled from the card, which is signalled by a "1" on the terminal21TB of the receiving circuit in the passive equipment. The charge unitycredit register 21CRTB is then incremented by one unity, and the balancein charge unities becomes nil. Terminal 21TB resets the coinage creditand debit registers 26CRM and 26DM via diode 266. The balance in coinagethen becomes nil. Transmission of the collection order is stopped.

The communication is continued using the charge unity balance. If theuser again changes his payment mode, either by removing his card, orbecause it has no credits left, automatically implying payment withcoins according to the process already described relative to switchingcircuit 14, the user then uses coins. Provided that the prior chargeunity balance is not negative, the communication continues withouttransmission of a collection order.

Thus at the moment the user decides to change the payment mode, thecredit remaining is not lost. As soon as this credit is exhausted,collection is effected with the other payment mode, the creditcorresponding to the coins newly inserted is entered in register 26CRM,while the charge unity debit and credit registers 26DTB and 26CRTB arereset after collection. These operations do not influence a card chargeunity totalizer-register 26TTB and a coinage totalizer-register incircuit 26 having inputs connected to terminal 21TB and terminals 21P₁to 21P₄ respectively. The totalizers-registers add, until the nextwithdrawal of the coin box which resets the totalizer registers, thedigits entered in credit registers 26CRTB and 26CRM, as thecommunications and various payment modes continue.

The payment mode can thus be changed during the course of thecommunication as many times as one wishes and in any direction. It canbe done at any moment without, on the one hand, the credit remainingbeing lost for the user and, on the other, the debit in the old accountbeing lost at this changeover of account. The debit is exactlytransferred to the account of the new mode of payment. It is only aftera collection order that the credit and debit registers corresponding tothe old mode of payment are reset.

The debit register for the payment mode not used is incremented by oneunity upon reception of each charge pulse, and the debit and creditregisters for the payment mode not used are reset at each collectionaccording to the payment mode used. In this way, registers are alwaysready for a change in the payment mode.

The coinage credit and debit register 26CRM and 26DM, and the chargeunity credit and debit registers 26CRTB and 26DTB keep and cumulate forthe payment mode which concerns them respectively, an account of thecommunication in progress alone and for a period of time correspondingto a payment mode without changeover.

(E2) If passive equipment 1 receives a collection order when the storageslides contain no more coins or when the prepaid card inserted has nomore charge unity credit, output 14P/C of switching circuit 14 is at "0"and output 160 of reception circuit 16 is at "1", in reference to FIG.3. The output of gate 151₁ controls stoppage of transmission of standbyfrequency F₁, which is indicated in active equipment 2 by a "0" atoutput 21V of receiving circuit 21.

As shown in FIG. 6B, terminal 21V is connected to the trigger input D₂of timer 271₂ through inverter 273₁ and the reset input RZ₂ of timer271₂, but also through inverter 273₁ to inputs of AND gate 274₁ and atwo-input AND gate 274₆. Another input of gate 274₆ as well as an inputof a two-input AND gate 274₇ and an input of a two-input AND gate 274₄are connected to output 220E of AND gate 263 in the charging checkingcircuit 26. Other inputs of gates 274₇ and 274₄ are connected to outputsS₂₂ and S₂₁ respectively of timer 271₂.

When terminal 21V is going from "1" to "0" in response to a collectionorder without presence of coins or card, or in presence of a card withnil credit, timer 271₂ is triggered. Simultaneously, an output of gate274₆ passes to "1", one of the inputs of this gate connected to theoutput of AND gate 263 being at "1" because of a negative balance. Theoutputs of gate 274₆ and terminal 27TON are connected to a base of atransistor 272₃ via a diode 275₄ and a monostable flip-flop 278₃self-triggerable by a 300 ms period and via a diode 275₅ respectively.The 300 ms pulses delivered by flip-flop 278₃ thus triggered modulatethe 1250 Hz clock frequency and are applied to transformers 206 and 207through a decoupling transformer 279 in order to transmit the "no morecredit" tone to passive equipment 1 and the "please hold" tone to thecalled party via switchboard CT.

At the end of time delay t₂₁ =6 s following triggering of timer 271₂,output S₂₁ opens gate 274₄ whose one output, via an inverter 273₄, turnsoff transistor 272₄ having a collector connected to terminal 2021 oftelephone blocking circuit 202. Diodes 2020 then momentarily interruptthe voice signals exchanged between the user and the called party.

Then after a period of 7 s, i.e. after time delay t₂₂ =13 s followingtriggering of timer 271₂, output s₂₂ of timer 271₂ passes to "1" if thebalance still remains negative and if no coins or card with credit havebeen inserted into the passive equipment. An output of AND gate 274₇being connected to the trigger input D₃ of timer 271₃ via OR gate 276₁,output S₃ of time delay device 271₃ passes to "0" during t₃ =6 s, whichdeactivates the power supply relay 2033, and the passive equipment powersupply is then cut off, which terminates the telephone communication.

Normally, the power supply to the passive equipment is cut off betweent₂₂ =13 s and t₂₂ +t₃ =19 s following triggering of timer 271₂ whichonly returns to zero after time delay t₂₂ +t₃ and thus after restorationof the power supply to the passive equipment; the standby frequency F₁is again transmitted, timer 271₂ returns to zero, and the equipments arein the rest phase.

However, if frequency F₁ is not transmitted after time delay t₂₂ +t₃ =19s, following an incident during this time delay, such as a line break orfailure of means 150₁ for transmitting frequency F₁, timer 271₂continues the time delay, and after t₂₃ =26 s, turns off transistor272₁, which definitively cuts off the power supply to the passiveequipment which is then in the out-of-service mode. Output 28A₁ thensignals an anomaly. The power supply is then restored from themanagement computer OG, and a brief pulse is applied to input 28R, asalready stated.

However, in response to the "no more credit" tone during time delay t₂₂-t₂₁ =7 s, if the user inserts one or more coins or a card with creditremaining, and terminal 21V returns to "1", thus resetting timer 271₂,transistor 272₄ is in conductive condition to re-establish an exchangeof voice signals. Validation of the collected coin or debiting of acharge unity increments the credit register 26CRM or 26CRTB and thebalance again becomes positive, which closes gate 263 and stopstransmission of frequency F₆ to the passive equipment.

(F) Hook-on by the called party

Hook-on by the called party causes a second battery reversal detected bythe voltage reversal and break detecting 25, reception of a busy tone bythe calling user and disconnection of corresponding links, notably inswitchboard CT. In response to the second battery reversal, outputterminal 25IB of circuit 25 passes from "1" to "0".

Monostable flip-flop 278₂ in monitor 27 detects a rising pulse edgeapplied by terminal 25IB and triggers timer 271₃ via OR gate 276₁.Output S₃ of timer 271₃ blocks transistor 272₁ which establishes a powersupply break to the passive equipment for t₃ =6 s. Any coins present inthe storage slides of mechanism 11 are refunded and/or a card present inmechanism 13 is ejected. After time delay t₃, the passive and activeequipments are at rest.

(G) "Hook-on" by the calling user

As already stated, the end of a communication is established normally,either by absence of coins in mechanism 11 and absence of prepaid cardin mechanism 13, or by the presence of a card with nil credit inmechanism 13, or by hook-on by the calling user.

Hook-on by the calling user in the passive equipment is normallycontrolled by pressing button 115 (FIG. 2A). This causes refunding ofcoins and/or ejection of the card, resulting from the "no more credit"condition and collection order received. The previously described phaseE2 is then completed in order to move on to either rest phase A orplacing of the active equipment in out-of-service mode. Phase E2 isshortened if the called party hooks-on before expiry of time delay t₂₂=13 s in timer 271₂ triggered by cessation of transmission of frequencyF₁. In this latter case, the previous phase F is established.

(H) Called party busy or selection incident

A situation of this nature was described with reference to the end ofthe dialling and selection phase C.

(I) No reply from called party; coins or card inserted without dialling

If the called party does not hook-off, or the calling user pressesbutton 115 (FIG. 2A) before the end of time delay t₁ =130 s in timer271₁ triggered by insertion of a coin or a card with credit remaining,phase G is accomplished. However, if time delay t₁ =130 s expires afterinsertion of a coin or a card with credit remaining, preceding orotherwise a dialling phase less than t₁ without hook-off by the calledparty, counter 277 is incremented by one unity by output S₁ of timer271₁ and output 21DEC of gate 215₇ at "1". Counter 277 will signal apublic telephone out-of-service mode after eight such consecutive callattempts, via terminal 28A₃.

Withdrawing the coin box; Break-in of coin box

In passive equipment 1, opening of the coin box compartment 110 openingcontact 117, or withdrawl of the coin box form compartment 111 openingcontact 118, causes transmission of frequencies F₃ and F₅ by the passiveequipment (FIGS. 2 and 3), in all normal or abnormal circumstances.

In the active equipment, the detection of at least one of the twofrequencies F₃ and F₅ by OR gate 216 (FIG. 5) triggers timer 271₁ inmonitor 27. The two frequencies F₃ and F₅ are also detected by AND gate215₆ (FIG. 5) having an output connected to another input of AND gate274₄ in the monitor. Opening of gate 215₆ also controls a transfer ofinformations stored in the registers of the storing circuit 28 to themanagement computer, as will be seen hereinafter.

In addition, in the passive equipment, opening of one of contacts 117and 118 interrupts the 6 V power supply to the collection mechanisms 11and 13, as shown in FIG. 2A. This power supply interrupt prevents atelephone communication being established by the collection personnel oranyone else, when coin box compartment 110 is open. Furthermore, thecontent of the registers in the charging checking circuit 26 remainfixed during transfer to the management computer.

The management computer OG receives and records "coin box withdrawal"information in the form of amounts of money and charge unities cumulatedin the totalizers-registers 26TM and 26TTB since the last passage andrecorded in the storing circuit via terminals 28TM and 28TTN (FIG. 8). Aprogram in a programmable memory attached to the computer OG isconsulted by the computer to read a list of collection staff passageintervals for the public telephone apparatuses, intervals which may beas short as one wishes. By detecting from the list the telephoneapparatus address, which transmitted a "coin box withdrawal" informationvia terminal 21A by comparing the actual moment of withdrawal with thecorresponding time interval on the list, the computer OG decides whetheropening of the coin box compartment via terminal 21A is normal orfraudulent.

In the event of fraudulent opening, the computer initiates a programmedalert procedure for the transmission of alarms. Simultaneously, viastoring circuit 28 and terminal 28R, computer OG proceeds to place thetelephone apparatus in out-of-service mode. These procedures aredetailed below.

If the withdrawal of the coin box is considered to be normal, theamounts in cash and charge unities are taken from registers 26TM and26TTB and entered in storing circuit 28, as well as reset of theseregisters via output terminal 28RZ of circuit 28.

In a normal condition, opening of compartment 110 and withdrawal of thecoin box must take place in less that t₁ =130 s and should give rise tono anomalies for transmission to the computer OG. However, an anomalymay be transmitted to the computer OG when the coin box is full. Forthis purpose, charging checking circuit 26 (FIG. 8) comprises acomparator 26CTM constantly comparing the total amount of coinscollected since the last withdrawal, delivered by the output bus ofcounter 26TM, with the maximum amount which the coin box can contain,delivered by output but 33TM from central memory 33 (FIG. 4). An anomalyinput 28A₇ of storing circuit 28 is set to "1" by an output ofcomparator 26CTM when the coin box in the apparatus is full. In thiscase, management computer OG places the apparatus in out-of-service modeand then re-establishes operation, via terminal 28R, when registers 26TMand 26TTB are reset to zero.

However, if following triggering of timer 271₁, output S₁ of this timerpasses to "1" at expiry of time delay t₁, output 28A₈ of AND gate 274₄passes to "1" and signals an withdrawal anomaly. In this case, thepassive equipment 1 is automatically placed in out-of-service mode bythe management computer OG. It is recalled that in the case of placingin out-of-service mode by computer OG, the public telephone apparatus isnevertheless returned to service manually and should be done fromcomputer OG by an operator following a process described further on,with reference to memory 28, in order to avoid automatic restoration bymeans of contacts 117 and 118.

In addition, it is to be noticed that any transmission of one of thefrequencies F₂, F₃, F₄ and F₅ triggers timer 271₁ via OR gate 216. Thislayout ensures a systematic time check in the processing of allsignallings transmitted by the passive equipment 1. Thus, in the eventof a technical anomaly, triggering of timer 271₁ results in a "selectioninoperative" type message reflected by incrementation of counter 277 byone unity. Eight consecutive incidents of this type lead to signallingby terminal 28A₃ and the public telephone apparatus is placed inout-of-service mode.

Telephone apparatus called by another public or private telephoneapparatus

When the pubic telephone is called for an incoming communication, theactive equipment 2 receives a call ringing current at 80 V and 50 or 25Hz, through line terminals A₀ B₀ on the switchboard CT side. During thecall, voltage limiter 200₀ stops transmission of the ringing current,and a break in the battery power supply is detected by the voltagereversal and break detecting circuit 25 shown in FIG. 7. As alreadystated, a break in the power supply on the switchboard CT side impliesthat terminal 250 has switched from -24 V to 0 V and that there istherefore a "1" at output terminal 25AP of circuit 25.

In monitor 27 shown in FIG. 6B, terminal 25AP is connected to the baseof transistor 272₃ via a shunt capacitor 27C and a diode 275₆. The state"1" at terminal 25AP results in conducting of transistor 272₃ and thustransmission of a 1250 Hz ringing tone supplied by terminal 27TON, onthe one hand, to passive equipment 1 through transformers 279 and 206,and of the other, to the calling party through transformers 279 and 207.The ringing tone is broadcast by loudspeaker HP (FIG. 1A). It is alsotransmitted to the calling subscriber and clearly informs him that he iscalling a public telephone apparatus.

In addition, timer 251 in circuit 25 shown in FIG. 7 has been reset bythe battery power supply preceding the ringing tone. Timer 251 istriggered by the passage from "1" to "0" of its reset terminal RZ andthe passage from "0" to "1" of its trigger input D as soon as the powersupply is cut in response to the call. The time delay set by timer 251limits the duration of the ringing to the public telephone apparatus tot_(AP) =20 s. There are then two alternatives AP1 and AP2:

(AP1) A user close to the public telephone apparatus inserts a coinbefore expiry of time delay t_(AP). The coin will be refunded to him atthe end of the communication. Reception of the coin in one of thestorage slides in passive equipment 1 sets terminal 14P/C (FIGS. 2C and3) to "1" and opens gate 157 and triggers transmission of frequencies F₂to F₅, still together with standby frequency F₁, to active equipment 2.Frequencies F₂ to F₅ are transmitted throughout the duration of thecommunication, with triggering of timer 271₁, normally limiting thedialling phase for a called communication, here neutralized as explainedbelow. Terminal 21DEC passes to "1" and activates ringing and breakrelay 2053 (FIG. 4) in order to close contact 2052, as in the case of anoutgoing communication, which loops the line on the switchboard CT sideand informs the latter of called user hook-off. The switchboard CT stopstransmission of the ringing signal at 50 or 25 Hz in response to linelooping and proceeds to the first battery reversal initializing theconversation phase of the incoming communication. In circuit 25 (FIG.7), terminal 250 passes to 24 V, timer 251 is reset and stopped, theringing tone is halted by a "0" at terminal 25AP, and output Q offlip-flop 253 passes to "1" which, via output 25CAP of circuit 25 and ORgate 276₂ of the monitor (FIG. 6), resets, stops and thereforeneutralizes timer 271₁ throughout the duration of the incomingcommunication. Also, in the receiving and decoding circuit 21 shown inFIG. 5, output 21DEC of AND gate 215₇ at "1" holds the other AND gates215₁ to 215₆ closed through NOR gate 217, which inhibits the chargingchecking circuit 28.

However, if during the conversation phase of this incomingcommunication, break-in or abnormal removal of the coin box takes place,the 6 V power supply is cut by opening of contacts 117 and 118 ofcompartment 110 in passive equipment 1 (FIG. 2). As already stated,frequencies F₃ to F₅ are transmitted from the passive equipment toactive equipment 2 and signal an anomaly via monitor terminal 28A₈.Terminal 21DEC passes to "0" since the other frequencies F₂ and F₄ arenot transmitted. Transistor 272₂ in the monitor is turned off, relay2053 is deactivated, contact 2052 opens the line on the switchboard CTside and thus interrupts the incoming communication.

The end of the communication is triggered either by the calling partyhook-on, or by pressing in the refund button 115, as already describedin phases F and G. In particular, the second battery reversal triggersmonostable flip-flop 254 in circuit 25 (FIG. 7) and, subsequently,resetting of output Q of flip-flop 253 and terminal 25CAP which placesthe timer 271₁ on standby for a future outgoing or incomingcommunication.

(AP2) If no user inserts a coin before expiry of time delay t_(AP) =20s, in response to the ringing tone, output S of time delay device 251passes to "1". This output S is connected to output terminal 25D/R ofcircuit 25 and also to an input of gate 258 via inverser 259.

State "1" of terminal 25D/R turns on transistor 272₂ in monitor 27 (FIG.6A) via diode 275₇ which simulates user hook-off by closing the ringingand break contact 2052 and thus triggers a first battery reversal byswitchboard CT. Furthermore, state "1" of terminal 25D/R holds gate 258closed and thus inhibits a battery reversal pulse delivered fromterminal 25IB to monitor 27 and to charging checking circuit 26 during anormal communication.

However, the first battery reversal sets terminal 250 in circuit 25 to-24 V, which resets timer 251 and therefore sets terminal 25D/R to "0"which turns off transistor 272₂ and opens contact 2052. The loop on theswitchboard CT side is again open, which simulates user hook-on.

Thus, after expiry of time delay t_(AP) =20 s, there is rapid andautomatic hook-off and hook-on. The rapidity of these actions depends onthe inertia in the ringing and break relay 2053 (FIG. 4) and results inno charge for the calling subscriber.

Call by the public telephone apparatus to a subscriber but withoutcharging

As for a normal call, the user should insert a coin or card in passiveequipment 1 so that active equipment 2 proceeds with hook-off byactivating relay 2053 (FIG. 4). Dialling a number but without chargingis similar to phase C, except that the time delay t₁ =130 s of timer271₁ triggered by transmission of frequencies F₂ to F₅ from passiveequipment 1 is not stopped by reception of frequency F₆ after hook-offby the called party, giving rise to initial battery reversal. In effect,no charge pulse is signalled to the charging checking circuit 26.Subsequently, the contents of debit registers 26DM and 26DC remain atzero and the balances are nil, which keeps AND gate 263 closed (FIG. 8).

A communication is thus established for the time remaining availablebefore expiry of time delay t₁ =130 s. In practice, the user has aconversation phase of about 100 s for a local call, 80 s for a trunkcall or 60 s for an international call. This duration is sufficient forthe user to transmit a brief message and ask to be called back.

As for a normal communication, the end of the non-chargeablecommunication is marked by second reversal of the battery, a cutoff ofthe 48 V power supply and the refund of the coin or ejectin of the cardinitially inserted, provided that the user has not already pressedrefund and ejection button 115.

STORING CIRCUIT

With reference to FIGS. 9A and 9B, storing circuit 28 comprises, inaddition to memory block 280, eighteen anomaly or similar memory blocks281₁ to 281₁₈, twelve memory blocks 282₁ to 282₁₂ for digits of thecoinage and charge unit totaliser accounts, one memory block for theout-of-service and in service modes 283, and one memory block 284 forresetting totalizer counters 26TM and 26TTB.

All data exchanged between the storing circuit 28, the link processor 3and the management computer OG are in the form of 4-bit binary words.Such a word permits encoding of each decimal digit 0 to 9 in atotalizer-count, the five remaining words being used for so-calledservice words A, B, C, D and E which will be defined subsequently. Theword "0000" is not used for security reasons.

Memory block 280 comprises a ROM memory containing the 10-bit addressword of the active equipment chosen from among 1024 address words foractive equipments managed by link processor 3. As already stated, 1024memory blocks 280 are fixed on a frame containing 1024 boards supportingthe active equipment circuits. Each memory block 280 is thus associatedwith a location of a board in the frame and thus allows to replace theboard when it is faulty, easily and quickly. Various connections betweenmemory blocks 280, central memory 33, link processor 3 and the otheractive equipment circuits are made by means of plug-in connectorsdenoted by CON in FIG. 4B. The memory block 280 also contains an one-bitRAM memory. This RAM memory signals, via read enable wire 285, to theother memory blocks 281₁ to 281₁₈, 282₁ to 282₁₈, 283 and 284, thatactive equipment 2 is called by processor 3 in response to the activeequipment 2 address delivered to ROM memory 280 by processor 3, via a10-wire bus 35.

Each anomaly memory block 281_(a), where integer a varies from 1 to 18,contains a 1-bit ROM memory connected to wire 285, and a 5-bit ROMmemory connected to a 5-wire block address bus 36 outputting fromprocessor 3. The 5-bit ROM contains the address of memory block 281_(a)in order to detect it on bus 36 together with a "1" on wire 285 and thusenable reading by processor 3 in three other 1-bit RAM memories includedin block 281_(a). The first RAM is connected to monitor 27 or to thecharging checking circuit 26 by a respective anomaly input terminal28A_(a), which, at state "1" calls processor 3. In fact, eight suchinputs 28A₁ to 28A₈ are used in the illustrated embodiment. The othertwo 1-bit RAMs in block 281_(a) are intended for signal exchanges withthe management computer via the link processor, for mainly reading thecontent of the first RAM, as will be seen later on. For this, the lasttwo RAMs of block 281_(a) are connected to two write wires 37₂ and 37₃outputting from processor 3, and the three RAMs of block 281 areconnected to three read wires 38₁, 38₂ and 38₃ inputting to processor 3.

Memory blocks 282₁ to 282₁₂ also each comprise a 1-bit ROM memoryconnected to wire 285, a 5-bit address RAM memory connected to blockaddress bus 36 and three 1-bit RAM memories having outputs connected toread wires 38₁ to 38₃. The inputs of the three RAMs in blocks 282₁ to282₁₂ are connected to the output terminal 21A of receiving circuit 21(FIG. 5) and to write wires 37₂ and 37₃ respectively. When terminal 21Ais at state "1", following a normal withdrawal of the coin box, a 4-bitword representing a totalizer-counter account digit is written in afour-cell RAM memory, also included in memory block 282₁ to 282₁₂. Thus,six 4-bit RAM memories included in blocks 282₁ to 282₁₂ memorize the sixbinary code digits delivered by the coinage totalizer-counter 26TM viabus 28TM having 6×4=24 wires, and six 4-bit RAM memories in blocks 282₇to 282₁₂ memorize the six binary code digits delivered by the chargeunity totalizer-counter 26TTB via bus 28TTB having 6×4=24 wires.

The 4-bit RAMs in blocks 282₁ to 282₁₂ each deliver the correspondingbinary code digit to processor 3 via an input read 4-wire bus 39, inresponse to the corresponding address on bus 36.

Control memory blocks 283 and 284 each also include a 1-bit ROM memoryand a 5-bit ROM memory connected to wire 285 and to block address bus 36respectively. In addition, each block 283 and 284 contains a 1-bit RAMmemory having a write input connected to wire 37₃ and an erase inputconnected to wire 37₂. A read output of memory RAM 283 is connected tothe monitor restoration terminal 28R, and a read output of memory RAM284 is connected to the reset terminals 28RZ of totalizers-counters 26TMand 26TTB.

The 32 memory blocks 281₁ to 281₁₈, 282₁ to 282₁₂, 283 and 284 in the1024 active equipments are cyclically explored by a 10+5=15 stagecounter included in a link processor 3. An active equipment is addressedby the 10 bits delivered on bus 35, which addresses the abovementioned32 memory blocks in this equipment, and each of these blocks isaddressed in turn by bus 36. A time base of about 60 kHz included inprocessor 3 sets an exploration cycle of about 500 ms, and a memoryblock interrogation time of about 15 microseconds.

In each memory block 281₁ to 281₁₈ and 282₁ to 282₁₂, each of the three1-bit RAMs memories the state of its input, either a "1" indicating ananomaly, a coin box withdrawal or a processor processing phase, or a "0"indicating an erasure of preceding information. The inputs of thesethree RAMs are data and write enable inputs. However, in each controlmemory block 283 and 284, wire 37₂ is connected to an erase input of the1-bit RAM in order to erase the "1" bit written via the data input ofthis 1-bit RAM connected to wire 37₃. Whenever wire 285 is at "1", andan address is present on bus 36, the processor enables reading ofinformation in the RAMs of the addressed memory block.

The following table I gives the signallings for processing of an anomalystored in a block 281₁ to 281₁₈ by link processor 3, with reference tothe states of wires 38₁, 38₂ and 38₃.

                  TABLE I                                                         ______________________________________                                        38.sub.1                                                                           38.sub.2                                                                            38.sub.3                                                                             Phase of link processor 3                                   ______________________________________                                        0    0     0      No anomaly to be transmitted                                1    0     0      Anomaly to be transmitted                                   1    1     0      Anomaly undergoing processing                               1    1     1      Anomaly transmitted and received by the                                       management computer OG with                                                   acknowledgement                                             0    1     1      Cause of anomaly disappeared                                                  Call to computer OG by processor                            0    0     1      Restoration of active equipment 2                                             corresponding to the end of the anomaly                                       transmitted to computer OG and received by                                    it                                                          0    0     0      Return to rest                                                                No anomaly to be transmitted                                ______________________________________                                    

For the above signallings, the information transmitted by processor 3 tocomputer OG is in the form of a stream of 10 half-octets comprising:

the 3-binary-coded-digit-address-of the processor for example;

the 4-binary-coded-digit-address of the equipment, between 0001 and1024;

the 2-binary-coded-digit-address of the anomaly memory block between 01and 18; and

a 4-bit "Service A" word for anomaly to be written and start of message;or

a 4bit "Service B" word for restoration of active equipment and start ofmessage; or

a 4-bit "Service C" word for acknowledgment, in both directions oftransmissions; or

a 4-bit "Service D" word for please-repeat-message request in bothdirections of transmission; or

a 4-bit "Service D" word for end-of-message, in both directions oftransmission.

The computer translates the received signalling word and performs,according to the selected program, the processing planned for thissignalling. It in particular makes the distinction between a signallingto be written (Code A) or a restoration and end-of-signalling (Code B).

The operation of blocks 282₁ to 282₁₂ is identical to that of blocks281₁ to 281₁₈ with regard to the addressing and management of theprocessor call by a block. For each of these blocks 282₁ to 282₁₂ thereis added the writing or reading of a half-octet in the RAM memorycorresponding to a decimal digit to be transmitted. The call order toprocessor 3 is given for all these 12 blocks by a "1" at terminal 21Arecorded in the first associated 1-bit RAMs. The procedure and thephases encountered in the event of an anomaly are given here. Only thecontent of each signalling message is supplemented by the 4 bits of thedigit to be transmitted.

In addition, and for this type of signalling only, when the 12 digitshave been transmitted and received by the computer OG under the controlof processor 3, the processor marks the RAM of block 284 with a "1" viawire 37₃. Output 28RZ of this RAM controls resetting of the coinage andcharge unity totalizers-counters 26TM and 26TTB in the charging checkingcircuit 26 of the active equipment concerned (FIG. 8). The simultaneousresetting of these 12 digits, checked on return by processor 3 via bus39, enables it to check that the totalizers-counters have in fact beenreset. Once this check is done, processor 3, via wire 37₂, erases thereset order entered in the RAM of block 284. The state of RAM 284 andoutput 28RZ returns to "0".

The following Table II gives the signalling for processing of atotalizer-counter digit by link processor 3, with reference to readoutput wires 38₁, 38₂ and 38₃. The states of terminal 21A and writeinput wires 37₂ and 37₃, as well as the reset terminal 28RZ fortotalizer counts 26TM and 26TTB are also given.

                                      TABLE II                                    __________________________________________________________________________    38.sub.1                                                                        38.sub.2                                                                         38.sub.3                                                                        Phase of link processor 3                                                                      21A                                                                              37.sub.2                                                                         37.sub.3                                                                         28RZ                                         __________________________________________________________________________    0 0  0 No digit to be transmitted                                                                     0  0  0  0                                            1 0  0 Coin box withdrawal or incident.                                                               1  0  0  0                                                   Digit to be transmitted                                                1 1  0 Digit undergoing processing.                                                                   1  0  0  0                                                   Link process undertaken                                                                        or                                                           by the processor 0                                                     1 1  1 Transmitted digit received                                                                     1  0  0  0                                                   by the computer with acknow-                                                                   or                                                           ledgement                                                              1 1  1 Order to reset totalizer                                                                       1  0  1  1                                                   counters 26TM and 26TTB                                                                        or                                                                            0                                                     1 1  1 Check by processor of                                                                          1  1  1  1                                                   resetting of 4-bit RAMs. If                                                                    or                                                           bus 39 at "0", marking of "1"                                                                  0                                                            on wire 37.sub.2 ; reset done and                                             checked; end of processing                                             1 1  1 1st case: terminal 21A at                                                                      1  1  1  1                                                   "1"  and coin box compartment                                                 open; stoppage processing                                                     under anomaly                                                          0 0  0 2nd case: terminal 21A at                                                                      0  0  0  0                                                   "0" and coin box compartment                                                  in normal operation,                                                          return to rest                                                         __________________________________________________________________________

It will be noted that contrary to the case of anomaly signalling, digitsignalling is marked in the first 1-bit RAMs of the respective block282₁ to 282₁₂ by a short pulse via terminal 21A, the state "1" thuswritten only being erasable by processor 3 at the end of processing ofthis signalling.

In the case of an anomaly, the disappearance of the signalling has to belocated and noted. In the case of a digit, the opening of the coin boxcompartment is to be noted and recorded, however short its duration, isin order to avoid fraud by manipulation of contacts 117 and 118 in thecoin box compartment 110. Taking account the duration of the scanningcycle, the computer OG records this signalling if it has a duration ofat least 500 ms. The coin box compartment opening and closing check aswell as the out-of-service command decided by the computer OG depend onthe signallings already seen, via terminals 28A₈ and 28R.

The charging checking circuit 26 in the active equipment is inhibitedduring the processing of digit signallings by an output 28ICT of thefirst 1-bit RAM of one of blocks 282₁ to 282₁₂, such as block 282₁₂, asshown in FIG. 9, connected to an input of the NOR gate 271 which closesor opens AND gates 215₁ to 215₆ (FIG. 5).

The purpose of this inhibition is to avoid disturbing the chargingchecking circuit 26 in the possible event in which the "digit"signalling processing terminates well after closure of compartment 110,following normal withdrawal of the coin box or breaking into thecompartment. Indeed, a return to the service of the public telephoneapparatus could be followed by resetting of the totalizers-counters thusentailing a loss of informations, since the transmission time for thedata from processor 3 to the computer OG essentially depends on the timetaken to establish a communication, generally about 10 to 40 seconds,whereas message transmission in the case of the 12 digits and thus 184bits takes less than one second (transmission rate of 200 Bauds).

The rapidity of the processor 3 exploration cycle will make the additionof a buffer memory to the processor virtually pointless. Such a buffermemory is virtually constituted by the memory blocks in the activeequipment storing circuits. The risk of losing data in the case ofanomaly signallings is insignificant and would only mean that a veryfleeting signalling would not be noted. With regard to digitsignallings, the steps taken mean that the entire passiveequipment/active equipment system and, in particular, the chargingchecking circuit 26, is blocked throughout processing of signallingrelative to digits. The digit data cannot be modified or erasedthroughout this period and will be processed whatever its duration andeven several days later in the event of a serious incident affecting thelink 31 between processor 3 and management computer OG. As alreadymentioned, the processing of several signallings during a given cycle isguaranteed by means of the N-channel multiplexer 32 (FIG. 4).

In another embodiment, the majority of the active equipment 2 circuits,such as monitor 27 and the charging checking circuit, are inmicroprocessor form. Similarly, certain circuits in passive equipment 1,such as circuits 12 and 14 described previously in reference to discretecomponents, may also be in microprocessor form.

What I claim is:
 1. Control and surveillance system for a prepaymentpublic telephone apparatus connected to a telephone central office via atelephone line, comprising:a first equipment included in said apparatusand connected to said telephone line for transmitting signalling signalsindicating particularly an energization of said apparatus, a hook-off,an insertion of a prepaid credit token having indicia representing aprepaid credit into said apparatus, a collection of a part of a prepaidcredit on said prepaid credit token and apparatus operating anomalies,and receiving collection order signals carried on said telephone lineand ordering a collection of a part of a prepaid credit on said prepaidcredit token, and a second equipment interconnected across saidtelephone line between said apparatus and said central office receivingand being responsive to said signalling signals and detecting signalstransmitted from said central office to indicate (a) establishing, (b)breaking, and (c) interrupting phases of a telephone communication, aswell as (d) transmitting said collection order signals on said telephoneline, and (e) checking the operation of said apparatus and detectingsignals, said telephone line having between said first and secondequipments a frequency transmission band wider than a conventional voicetelephone frequency transmission band-width to transmit, withoutdisturbing said telephone communication, said signalling and collectionorder signals by transmitting carrier frequencies higher than telephonefrequencies in said conventional band.
 2. A system according to claim 1,wherein said second equipment comprises means for applying a dc voltageto said telephone line between said second and first equipments, andwherein said first equipment comprises means for power supplying saidfirst equipment from said dc voltage.
 3. A system according to claim 2,wherein said first equipment comprises means for transmitting a firstsignalling signal to said second equipment responsive to power supplyingof said first equipment, and wherein said second equipment comprisesmeans for receiving said first signalling signal and means for detectingtransmission and reception faults in said first signalling signal viasaid transmitting and receiving means during a predetermined period, andmeans for controlling said dc voltage applying means for stopping saidpower supply to said first equipment following faults detected by saiddetecting means during said predetermined period.
 4. A system accordingto claim 1, wherein said first equipment comprises means fortransmitting a second signalling signal to said second equipment as soonas said prepaid credit token is inserted into collection means of saidapparatus, said second equipment comprises means for looping saidtelephone line between said second equipment and said central office inresponse to said signalling signal, thereby simulating a hook-off withrespect of said telephone apparatus.
 5. A system according to claim 4,wherein said second equipment comprises means for briefly interrupting apower supply of the first equipment as soon as at least a part of saidsecond signalling signal is transmitted continuously for a secondpredetermined period following insertion of said prepaid credit token insaid collecting means.
 6. A system according to claim 4, wherein saidsecond equipment comprises means for definitively stopping the powersupply of the first equipment when said second signal is partiallytransmitted by the first equipment or partially received by said secondequipment for a second predetermined period following insertion of saidprepaid credit token into said collecting means, and wherein a cessationin said power supply of said first equipment triggers refunding ofinserted and not collected prepaid credit token.
 7. A system accordingto claim 4, wherein said second equipment comprises counting means fordefinitively stopping a power supply of said first equipment when saidsecond signalling signal is partially received by the second equipmentfor a second predetermined period and repeated after a predeterminednumber of successive prepaid credit token insertions into the collectingmeans, and wherein a cessation in said power supply of said firstequipment triggers a refunding of inserted and not collected prepaidcredit token.
 8. A system according to claim 1, wherein said apparatuscomprises means for delivering dialing pulses, and said first equipmentcomprises means for transmitting a third signalling signal modulated bysaid dialling pulses to said second equipment, and wherein said secondequipment comprises means for demodulating said dialing pulses intodemodulated dialing pulses and means for looping and unlooping saidtelephone line between said second equipment and said telephone centraloffice in response to said demodulated dialing pulses.
 9. A systemaccording to claim 1, wherein said second equipment comprises means forbriefly interrupting a power supply of said first equipment andtriggering refunding of a prepaid credit on said prepaid credit tokennot collected from said apparatus, when said second equipment does notreceive said response signal from a called party transmitted by saidcentral office, after a predetermined period following insertion of saidprepaid credit token into said apparatus.
 10. A system according toclaim 1, wherein said second equipment comprises means for detecting aresponse signal from a called party transmitted by said central office,such as a first battery reversal, and means for holding a line loopbetween said second equipment and said central office following saiddetected response signal.
 11. A control and surveillance system for aprepayment public telephone apparatus connected to a telephone centraloffice via a telephone line, comprising:a first equipment included insaid apparatus and connected to said telephone line for transmittingsignalling signals indicating particularly an energization of saidapparatus, a hook-off, an insertion of a prepaid credit token havingindicia representing a prepaid credit into said apparatus, a collectionof a part of a prepaid credit on said prepaid credit token and apparatusoperating anomalies, and receiving collection order signals carried onsaid telephone line and ordering a collection of a part of a prepaidcredit on said prepaid credit token, and a second equipmentinterconnected across said telephone line between said apparatus andsaid central office receiving and being responsive to said signallingsignals and detecting signals transmitted from said central office toindicate (a) establishing, (b) breaking, and (c) interrupting phases ofa telephone communication, as well as (d) transmitting said collectionorder signals on said telephone line, and (e) checking the operation ofsaid apparatus and detected signals, said telephone line having betweensaid first and second equipments a frequency transmission band widerthan a conventional voice telephone frequency transmission band-width totransmit, without disturbing said telephone communication, saidsignalling and collection order signals by transmitting carrierfrequencies higher than telephone frequencies in said conventional band,and said second equipment comprising means for detecting charge pulsestransmitted by said central office, and charging checking means forconstantly evaluating a communication balance as a function of a numberof charge pulses and said prepaid credit token inserted into saidapparatus throughout a conversation phase of said communication and forbreaking off said communication after said balance has been negative fora third predetermined period.
 12. A system according to claim 11,wherein said first equipment comprises means for collecting saidtransmitting one of signalling signals representative of collected cointo said second equipment in response to one of said collection ordersignal transmitted by the second equipment, and wherein said chargingchecking means comprises first means for calculating a firstcommunication debit by cumulating the value of a basic charge unity inresponse to each detected charge pulse, first means for calculating afirst communication credit by adding the values of collected coinsduring the communication in response to said signalling signalsrepresentative of collected coins respectively, first means forestablishing a first communication balance equal to the differencebetween the first credit and debit, and means for transmitting saidcollection order signal to said first equipment whenever said balance isnegative.
 13. A system according to claim 12, wherein said collectingmeans comprises means for detecting abnormal routing of each collectedcoin between a coin storage zone and a collected coin receptacle, andmeans for replacing said signalling signal representative of collectedcoins by an anomaly signal transmitted to said second equipment when anabnormal routing of said collected coin is being detected.
 14. A systemaccording to claim 11, wherein said first equipment comprises means forcollecting said prepaid credit token in the form of cancellation ofcharge unities from a prepaid card, and means for transmitting asignalling signal representative of a cancelled charge unity to saidsecond equipment in response to said collection order signal transmittedby said second equipment, and wherein said charging checking meanscomprises second means for calculating a second communication debit byadding one unity in response to each detected charge unity pulse, secondmeans for calculating a second credit communication by adding a unit inresponse to each signalling signal representative of a cancelled chargeunit, second means for constantly establishing a second balance of saidcommunication equal to the difference between said second debit andcredit, and means for transmitting said collection order signal wheneversaid second balance is negative.
 15. A system according to claim 12,wherein said second equipment comprises means for briefly breaking apower supply of said first equipment upon expiry of a secondpredetermined period during which said collection order signal istransmitted without the second equipment receiving any one of saidcollected coin representative signalling signals.
 16. A system accordingto claim 12, wherein said first equipment comprises means for signallingan absence of said prepaid credit token in said collecting means in saidsecond equipment in response to each collection order signal, andwherein said second equipment comprises means for transmitting a calledparty tone to said first equipment during no longer than a thirdpredetermined period and as long as a balance of said communicationremains negative, and means for interrupting voice signals carried bysaid telephone line for at most at most a fourth predetermined periodpreceding the end of said first predetermined period when said balanceremains negative.
 17. A system according to claim 12, wherein said firstequipment comprises means for collecting coins of various values in aremovable receptacle in a closing compartment, means for detectingopening of the compartment and removal of said receptacle from thecompartment, and means for transmitting a signalling signal indicatingopening of said compartment and removal of said receptacle to saidsecond equipment, and wherein said second equipment comprises means fordetecting said opening and removal signalling signal thereby signallingopening of said compartment and removal of said receptacle.
 18. A systemaccording to claim 17, wherein said opening and removal detecting meansbreaks the power supply of said collecting means as soon as said openingand removal is detected, so as to prevent establishment of saidreceptacle.
 19. A system according to claim 12, wherein said chargingchecking means comprises means for totalizing said first communicationcredits between two successive openings and removals, means for readinga totalized amount in said totalizing means in response to said openingand removal signalling signal, and means for transmitting said totalizedamount to remote management means through a telephone network, as soonas said opening and removal signalling signal is detected in said secondequipment.
 20. A system according to claim 17, wherein said secondequipment comprises means for placing said first equipment inout-of-service mode by cutting off a power supply of said firstequipment when said opening and removal signalling signal is received bysaid second equipment for longer than a fifth predetermined period. 21.A system according to claim 17, wherein said charging checking meanscomprises means for totalizing said first communication credits betweentwo successive openings and removals and means for comparing the totalof the first totalized credits with a predetermined amount in order tosignal that the receptacle is full with coins.
 22. A control andsurveillance system for a prepayment public telephone apparatusconnected to a central office via a telephone line, comprising:a firstequipment included in said apparatus and connected to said telephoneline for transmitting signalling signals indicating particularly anenergization of said apparatus, a hook-off, an insertion of a prepaidcredit token having indicia representing a prepaid credit into saidapparatus, a collection of a part of a prepaid credit on said prepaidcredit token and apparatus operating anomalies, and receiving collectionorder signals carried on said telephone line and ordering a collectionof a part of a prepaid credit on said prepaid credit token, and a secondequipment interconnected across said telephone line between saidapparatus and said central office receiving and being responsive to saidsignalling signals and detecting signals transmitted from said centraloffice to indicate (a) establishing, (b) breaking, and (c) interruptingphases of a telephone communication, as well as (d) transmitting saidcollection order signals on said telephone line, and (e) checking theoperation of said apparatus and detected signals, said telephone linehaving between said first and second equipments a frequency transmissionband wider than a conventional voice telephone frequency transmissionband-width to transmit, without disturbing said telephone communication,said signalling and collection order signals by transmitting carrierfrequencies higher than telephone frequencies in said conventional band,and said second equipment comprising means for detecting a calling partyringing signal transmitted by said central office in order to establishan incoming communication and means for transmitting a ringing tone tothe first equipment, broadcast by a loudspeaker in said apparatus, andto said central office to indicate a public telephone apparatus call toa caller party.
 23. A system according to claim 22, wherein said ringingtone is transmitted for no longer than a fifth predetermined period. 24.A system according claim 23, wherein said first equipment comprisesmeans for transmitting a second signalling signal to said secondequipment when a prepaid credit token is inserted into collecting meansof said apparatus before expiry of said first predetermined period, andwherein said second equipment comprises means for looping the telephoneline on said central office in response to said second signalling signalthereby simulating user hook-off and stopping said ringing signal.
 25. Asystem according to claim 24, wherein said second equipment comprisesmeans for detecting charge pulses transmitted by said central office,and charging checking means for constantly evaluating a communicationbalance as a function of a number of charge pulses and said prepaidcredit token inserted into said apparatus throughout a conversationphase of said communication and for breaking off said communicationafter said balance be negative for a second predetermined period, andmeans for inhibiting charging checking means in response to said secondsignal.
 26. A system according to claim 24, wherein said secondequipment comprises means for looping and unlooping the telephone lineon said central office when said second signal is not detected duringsaid first predetermined period.
 27. A system according to claim 1,wherein said public telephone apparatus comprises a handset having anearpiece and a microphone, a fixed loudspeaker and a fixed microphone,and means, manually activated when the handset is grasped, forcontrolling switching means selectively connecting said earpiece andsaid microphone of said handset and said fixed loudspeaker andmicrophone to said telephone line.
 28. A control and surveillance systemfor a prepayment public telephone apparatus connected to a telephonecentral office via a telephone line, comprising:a first equipmentincluded in said apparatus and connected to said telephone line fortransmitting signalling signals indicating particularly an energizationof said apparatus, a hook-off, an insertion of a prepaid credit tokenhaving indicia representing a prepaid credit into said apparatus, acollection of a part of a prepaid credit on said prepaid credit tokenand apparatus operating anomalies, and receiving collection order signlscarried on said telephone line and ordering a collection of a part of aprepaid credit on said prepaid credit token, and a second equipmentinterconnected across said telephone line between said apparatus andsaid central office receiving and being responsive to said signallingsignals and detecting signals transmitted from said central office toindicate (a) establishing, (b) breaking, and (c) interrupting phases ofa telephone communication, as well as (d) transmitting said collectionorder signals on said telephone line, and (e) checking the operation ofsaid apparatus and detected signals, said telephone line having betweensaid first and second equipments a frequency transmission band widerthan a conventional voice telephone frequency transmission band-width totransmit, without disturbing said telephone communication, saidsignalling and collection order signals by transmitting carrierfrequencies higher than telephone frequencies in said conventional band,and said second equipment comprising means for transmittingpredetermined signals to remote management means via a telephonenetwork, said predetermined signals operating anomalies in said firstequipment and an excessive communication cost, respectively.
 29. Asystem according to claim 28, wherein said operating anomaly consistsof:a transmission fault in said first equipment and reception fault insaid second equipment concerning a first signalling signal transmittedalmost permanently by said first equipment, abnormal attenuation andbreakage of the telephone line between said equipments, a transmissionfault in said first equipment or reception fault in said secondequipment and reception fault in said second equipment concerning atleast a part of a second signalling signal transmitted by said firstequipment following a hook-off phase simulated by insertion of a prepaidcredit token having indicia representing a prepaid credit intocollecting means of said apparatus in said first equipment, apredetermined number of consecutive fruitless call attempts, withoutexchange of voice signals from said first equipment, each of theattempts exceeding a first predetermined period, a collection faultconcerning part of a prepaid credit on said prepaid credit tokeninserted into said first equipment following transmission of acollection order signal by said second equipment to said first equipmentfor at least a second predetermined period, opening of a compartmentcontaining a coin receptacle in said apparatus, and withdrawal of saidreceptacle from said compartment during at least a third predeterminedperiod.
 30. A system according to claim 28, wherein said excessivecommunication cost consists ofa cost of a communication prepaid by coinscollected in said first equipment and exceeding a predetermined maximumcommunication cost, a cost of a communication prepaid by means of aprepaid card inserted into said first equipment and exceeding apredetermined maximum credit value available with a credit card, and anamount of coins collected in said receptacle in said first equipmentexceeding a predetermined maximum amount of coins which said receptacleis capable of containing.
 31. A system according to claim 14, whereinsaid second equipment comprises means for briefly breaking a powersupply of said first equipment upon expiry of a second predeterminedperiod during which said collection order signal is transmitted withoutsaid second equipment receiving said signalling signal representative ofa cancelled charge unity.
 32. A system according to claim 14, whereinsaid first equipment comprises means for signalling an absence of saidprepaid credit token in said collecting means in said second equipmentin response to each collection order signal, and wherein said secondequipment comprises means for transmitting a called party tone to saidfirst equipment during no longer than a third predetermined period andas long as a balance of said communications remains negative, and meansfor interrupting voice signals carried by said telephone line for atmost a fourth predetermined period preceding the end of said firstpredetermined period when said balance remains negative.